diff --git a/.babelrc.json b/.babelrc.json
new file mode 100644
index 0000000..ece1d87
--- /dev/null
+++ b/.babelrc.json
@@ -0,0 +1,5 @@
+{
+  "presets": [
+    ["@babel/preset-env"]
+  ]
+}
diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..d83d722
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,18 @@
+# This file is for unifying the coding style for different editors and IDEs
+# editorconfig.org
+
+root = true
+
+[*]
+end_of_line = lf
+charset = utf-8
+insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = space
+indent_size = 4
+
+[*.json]
+indent_size = 2
+
+[*.yml]
+indent_size = 2
diff --git a/.eslintignore b/.eslintignore
new file mode 100644
index 0000000..29af31d
--- /dev/null
+++ b/.eslintignore
@@ -0,0 +1,8 @@
+node_modules
+dist
+
+!.eslintrc.js
+coverage
+
+src/es5-identifier.js
+src/es6-identifier.js
diff --git a/.eslintrc.cjs b/.eslintrc.cjs
new file mode 100644
index 0000000..1507be3
--- /dev/null
+++ b/.eslintrc.cjs
@@ -0,0 +1,48 @@
+'use strict';
+module.exports = {
+    env: {
+        browser: true,
+        commonjs: true,
+        es6: true,
+        node: true
+    },
+    extends: 'eslint:recommended',
+    globals: {
+        Atomics: 'readonly',
+        SharedArrayBuffer: 'readonly'
+    },
+    overrides: [{
+        files: '.eslintrc.js',
+        parserOptions: {
+            sourceType: 'script'
+        },
+        rules: {
+            strict: 'error'
+        }
+    }, {
+        files: 'test/**',
+        globals: {
+            expect: true
+        },
+        env: {
+            mocha: true
+        }
+    }],
+    parserOptions: {
+        sourceType: 'module',
+        ecmaVersion: 2018
+    },
+    rules: {
+        semi: ['error'],
+        indent: ['error', 4, { SwitchCase: 1 }],
+        'prefer-const': ['error'],
+        'no-var': ['error'],
+        'prefer-destructuring': ['error'],
+        'object-shorthand': ['error'],
+        'object-curly-spacing': ['error', 'always'],
+        quotes: ['error', 'single'],
+        'quote-props': ['error', 'as-needed'],
+        'brace-style': ['error', '1tbs', { allowSingleLine: true }],
+        'prefer-template': ['error']
+    }
+};
diff --git a/.gitignore b/.gitignore
index 3c3629e..0e75fe5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,3 @@
 node_modules
+dist
+coverage
diff --git a/.jshintrc b/.jshintrc
deleted file mode 100644
index f642dae..0000000
--- a/.jshintrc
+++ /dev/null
@@ -1,16 +0,0 @@
-{
-  "curly": true,
-  "eqeqeq": true,
-  "immed": true,
-  "eqnull": true,
-  "latedef": true,
-  "noarg": true,
-  "noempty": true,
-  "quotmark": "single",
-  "undef": true,
-  "unused": true,
-  "strict": true,
-  "trailing": true,
-
-  "node": true
-}
diff --git a/.npmrc b/.npmrc
new file mode 100644
index 0000000..c1ca392
--- /dev/null
+++ b/.npmrc
@@ -0,0 +1 @@
+package-lock = false
diff --git a/.travis.yml b/.travis.yml
index 4b59f8d..c449b78 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,8 +1,5 @@
 language: node_js
 node_js:
-    - "0.10"
-    - "0.11"
-
-matrix:
-    allow_failures:
-        - node_js: "0.11"
+  - 12
+  - 14
+  - 16
diff --git a/README.md b/README.md
index e901aac..4deaf82 100644
--- a/README.md
+++ b/README.md
@@ -4,29 +4,29 @@ utility box for ECMAScript language tools.
 
 ## API
 
-## `ast` 
+## `ast`
 
-### `ast.isExpression(node)` 
+### `ast.isExpression(node)`
 
 Returns `true` if `node` is an `Expression` as defined in ECMA262 edition 5.1 section
 [11](https://es5.github.io/#x11).
 
-### `ast.isStatement(node)` 
+### `ast.isStatement(node)`
 
 Returns `true` if `node` is a `Statement` as defined in ECMA262 edition 5.1 section
 [12](https://es5.github.io/#x12).
 
-### `ast.isIterationStatement(node)` 
+### `ast.isIterationStatement(node)`
 
 Returns `true` if `node` is an `IterationStatement` as defined in ECMA262 edition
 5.1 section [12.6](https://es5.github.io/#x12.6).
 
-### `ast.isSourceElement(node)` 
+### `ast.isSourceElement(node)`
 
 Returns `true` if `node` is a `SourceElement` as defined in ECMA262 edition 5.1
 section [14](https://es5.github.io/#x14).
 
-### `ast.trailingStatement(node)` 
+### `ast.trailingStatement(node)`
 
 Returns `Statement?` if `node` has trailing `Statement`.
 ```js
@@ -35,7 +35,7 @@ if (cond)
 ```
 When taking this `IfStatement`, returns `consequent;` statement.
 
-### `ast.isProblematicIfStatement(node)` 
+### `ast.isProblematicIfStatement(node)`
 
 Returns `true` if `node` is a problematic `IfStatement`. If `node` is a problematic `IfStatement`, `node` cannot be represented as an one-to-one JavaScript code.
 ```js
@@ -54,101 +54,101 @@ Returns `true` if `node` is a problematic `IfStatement`. If `node` is a problema
 The above node cannot be represented as a JavaScript code, since the top level `else` alternate belongs to an inner `IfStatement`.
 
 
-## `code` 
+## `code`
 
-### `code.isDecimalDigit(code)` 
+### `code.isDecimalDigit(code)`
 
 Return `true` if provided code is decimal digit.
 
-### `code.isHexDigit(code)` 
+### `code.isHexDigit(code)`
 
 Return `true` if provided code is hexadecimal digit.
 
-### `code.isOctalDigit(code)` 
+### `code.isOctalDigit(code)`
 
 Return `true` if provided code is octal digit.
 
-### `code.isWhiteSpace(code)` 
+### `code.isWhiteSpace(code)`
 
-Return `true` if provided code is white space. 
+Return `true` if provided code is white space.
 White space characters are formally defined in ECMA262.
 
-### `code.isLineTerminator(code)` 
+### `code.isLineTerminator(code)`
 
-Return `true` if provided code is line terminator. 
+Return `true` if provided code is line terminator.
 Line terminator characters are formally defined in ECMA262.
 
-### `code.isIdentifierStart(code)` 
+### `code.isIdentifierStart(code)`
 
-Return `true` if provided code can be the first character of ECMA262 `Identifier`. 
+Return `true` if provided code can be the first character of ECMA262 `Identifier`.
 They are formally defined in ECMA262.
 
-### `code.isIdentifierPart(code)` 
+### `code.isIdentifierPart(code)`
 
-Return `true` if provided code can be the trailing character of ECMA262 `Identifier`. 
+Return `true` if provided code can be the trailing character of ECMA262 `Identifier`.
 They are formally defined in ECMA262.
 
-## `keyword` 
+## `keyword`
 
-### `keyword.isKeywordES5(id, strict)` 
+### `keyword.isKeywordES5(id, strict)`
 
 Returns `true` if provided identifier string is a Keyword or Future Reserved Word
-in ECMA262 edition 5.1. 
+in ECMA262 edition 5.1.
 They are formally defined in ECMA262 sections
 [7.6.1.1](http://es5.github.io/#x7.6.1.1) and [7.6.1.2](http://es5.github.io/#x7.6.1.2),
-respectively. 
+respectively.
 If the `strict` flag is truthy, this function additionally checks whether
 `id` is a `Keyword` or `FutureReservedWord` under strict mode.
 
-### `keyword.isKeywordES6(id, strict)` 
+### `keyword.isKeywordES6(id, strict)`
 
 Returns `true` if provided identifier string is a `Keyword` or `FutureReservedWord`
-in ECMA262 edition 6. 
+in ECMA262 edition 6.
 They are formally defined in ECMA262 sections
 [11.6.2.1](http://ecma-international.org/ecma-262/6.0/#sec-keywords) and
 [11.6.2.2](http://ecma-international.org/ecma-262/6.0/#sec-future-reserved-words),
-respectively. 
+respectively.
 If the `strict` flag is truthy, this function additionally checks whether
 `id` is a `Keyword` or `FutureReservedWord` under strict mode.
 
-### `keyword.isReservedWordES5(id, strict)` 
+### `keyword.isReservedWordES5(id, strict)`
 
 Returns `true` if provided identifier string is a `ReservedWord` in ECMA262 edition 5.1.
 They are formally defined in ECMA262 section [7.6.1](http://es5.github.io/#x7.6.1).
 If the `strict` flag is truthy, this function additionally checks whether `id`
 is a `ReservedWord` under strict mode.
 
-### `keyword.isReservedWordES6(id, strict)` 
+### `keyword.isReservedWordES6(id, strict)`
 
 Returns `true` if provided identifier string is a `ReservedWord` in ECMA262 edition 6.
 They are formally defined in ECMA262 section [11.6.2](http://ecma-international.org/ecma-262/6.0/#sec-reserved-words).
 If the `strict` flag is truthy, this function additionally checks whether `id`
 is a `ReservedWord` under strict mode.
 
-### `keyword.isRestrictedWord(id)` 
+### `keyword.isRestrictedWord(id)`
 
 Returns `true` if provided identifier string is one of `eval` or `arguments`.
 They are restricted in strict mode code throughout ECMA262 edition 5.1 and
 in ECMA262 edition 6 section [12.1.1](http://ecma-international.org/ecma-262/6.0/#sec-identifiers-static-semantics-early-errors).
 
-### `keyword.isIdentifierNameES5(id)` 
+### `keyword.isIdentifierNameES5(id)`
 
 Return `true` if provided identifier string is an `IdentifierName` as specified in
 ECMA262 edition 5.1 section [7.6](https://es5.github.io/#x7.6).
 
-### `keyword.isIdentifierNameES6(id)` 
+### `keyword.isIdentifierNameES6(id)`
 
 Return `true` if provided identifier string is an `IdentifierName` as specified in
 ECMA262 edition 6 section [11.6](http://ecma-international.org/ecma-262/6.0/#sec-names-and-keywords).
 
-### `keyword.isIdentifierES5(id, strict)` 
+### `keyword.isIdentifierES5(id, strict)`
 
 Return `true` if provided identifier string is an `Identifier` as specified in
-ECMA262 edition 5.1 section [7.6](https://es5.github.io/#x7.6). 
-If the `strict` flag is truthy, this function additionally checks whether `id` 
+ECMA262 edition 5.1 section [7.6](https://es5.github.io/#x7.6).
+If the `strict` flag is truthy, this function additionally checks whether `id`
 is an `Identifier` under strict mode.
 
-### `keyword.isIdentifierES6(id, strict)` 
+### `keyword.isIdentifierES6(id, strict)`
 
 Return `true` if provided identifier string is an `Identifier` as specified in
 ECMA262 edition 6 section [12.1](http://ecma-international.org/ecma-262/6.0/#sec-identifiers).
diff --git a/lib/ast.js b/lib/ast.js
deleted file mode 100644
index 8faadae..0000000
--- a/lib/ast.js
+++ /dev/null
@@ -1,144 +0,0 @@
-/*
-  Copyright (C) 2013 Yusuke Suzuki <utatane.tea@gmail.com>
-
-  Redistribution and use in source and binary forms, with or without
-  modification, are permitted provided that the following conditions are met:
-
-    * Redistributions of source code must retain the above copyright
-      notice, this list of conditions and the following disclaimer.
-    * Redistributions in binary form must reproduce the above copyright
-      notice, this list of conditions and the following disclaimer in the
-      documentation and/or other materials provided with the distribution.
-
-  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 'AS IS'
-  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
-  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
-  ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
-  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
-  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
-  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
-  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
-  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-*/
-
-(function () {
-    'use strict';
-
-    function isExpression(node) {
-        if (node == null) { return false; }
-        switch (node.type) {
-            case 'ArrayExpression':
-            case 'AssignmentExpression':
-            case 'BinaryExpression':
-            case 'CallExpression':
-            case 'ConditionalExpression':
-            case 'FunctionExpression':
-            case 'Identifier':
-            case 'Literal':
-            case 'LogicalExpression':
-            case 'MemberExpression':
-            case 'NewExpression':
-            case 'ObjectExpression':
-            case 'SequenceExpression':
-            case 'ThisExpression':
-            case 'UnaryExpression':
-            case 'UpdateExpression':
-                return true;
-        }
-        return false;
-    }
-
-    function isIterationStatement(node) {
-        if (node == null) { return false; }
-        switch (node.type) {
-            case 'DoWhileStatement':
-            case 'ForInStatement':
-            case 'ForStatement':
-            case 'WhileStatement':
-                return true;
-        }
-        return false;
-    }
-
-    function isStatement(node) {
-        if (node == null) { return false; }
-        switch (node.type) {
-            case 'BlockStatement':
-            case 'BreakStatement':
-            case 'ContinueStatement':
-            case 'DebuggerStatement':
-            case 'DoWhileStatement':
-            case 'EmptyStatement':
-            case 'ExpressionStatement':
-            case 'ForInStatement':
-            case 'ForStatement':
-            case 'IfStatement':
-            case 'LabeledStatement':
-            case 'ReturnStatement':
-            case 'SwitchStatement':
-            case 'ThrowStatement':
-            case 'TryStatement':
-            case 'VariableDeclaration':
-            case 'WhileStatement':
-            case 'WithStatement':
-                return true;
-        }
-        return false;
-    }
-
-    function isSourceElement(node) {
-      return isStatement(node) || node != null && node.type === 'FunctionDeclaration';
-    }
-
-    function trailingStatement(node) {
-        switch (node.type) {
-        case 'IfStatement':
-            if (node.alternate != null) {
-                return node.alternate;
-            }
-            return node.consequent;
-
-        case 'LabeledStatement':
-        case 'ForStatement':
-        case 'ForInStatement':
-        case 'WhileStatement':
-        case 'WithStatement':
-            return node.body;
-        }
-        return null;
-    }
-
-    function isProblematicIfStatement(node) {
-        var current;
-
-        if (node.type !== 'IfStatement') {
-            return false;
-        }
-        if (node.alternate == null) {
-            return false;
-        }
-        current = node.consequent;
-        do {
-            if (current.type === 'IfStatement') {
-                if (current.alternate == null)  {
-                    return true;
-                }
-            }
-            current = trailingStatement(current);
-        } while (current);
-
-        return false;
-    }
-
-    module.exports = {
-        isExpression: isExpression,
-        isStatement: isStatement,
-        isIterationStatement: isIterationStatement,
-        isSourceElement: isSourceElement,
-        isProblematicIfStatement: isProblematicIfStatement,
-
-        trailingStatement: trailingStatement
-    };
-}());
-/* vim: set sw=4 ts=4 et tw=80 : */
diff --git a/lib/code.js b/lib/code.js
deleted file mode 100644
index 23136af..0000000
--- a/lib/code.js
+++ /dev/null
@@ -1,135 +0,0 @@
-/*
-  Copyright (C) 2013-2014 Yusuke Suzuki <utatane.tea@gmail.com>
-  Copyright (C) 2014 Ivan Nikulin <ifaaan@gmail.com>
-
-  Redistribution and use in source and binary forms, with or without
-  modification, are permitted provided that the following conditions are met:
-
-    * Redistributions of source code must retain the above copyright
-      notice, this list of conditions and the following disclaimer.
-    * Redistributions in binary form must reproduce the above copyright
-      notice, this list of conditions and the following disclaimer in the
-      documentation and/or other materials provided with the distribution.
-
-  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
-  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
-  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
-  ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
-  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
-  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
-  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
-  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
-  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-*/
-
-(function () {
-    'use strict';
-
-    var ES6Regex, ES5Regex, NON_ASCII_WHITESPACES, IDENTIFIER_START, IDENTIFIER_PART, ch;
-
-    // See `tools/generate-identifier-regex.js`.
-    ES5Regex = {
-        // ECMAScript 5.1/Unicode v9.0.0 NonAsciiIdentifierStart:
-        NonAsciiIdentifierStart: /[\xAA\xB5\xBA\xC0-\xD6\xD8-\xF6\xF8-\u02C1\u02C6-\u02D1\u02E0-\u02E4\u02EC\u02EE\u0370-\u0374\u0376\u0377\u037A-\u037D\u037F\u0386\u0388-\u038A\u038C\u038E-\u03A1\u03A3-\u03F5\u03F7-\u0481\u048A-\u052F\u0531-\u0556\u0559\u0561-\u0587\u05D0-\u05EA\u05F0-\u05F2\u0620-\u064A\u066E\u066F\u0671-\u06D3\u06D5\u06E5\u06E6\u06EE\u06EF\u06FA-\u06FC\u06FF\u0710\u0712-\u072F\u074D-\u07A5\u07B1\u07CA-\u07EA\u07F4\u07F5\u07FA\u0800-\u0815\u081A\u0824\u0828\u0840-\u0858\u08A0-\u08B4\u08B6-\u08BD\u0904-\u0939\u093D\u0950\u0958-\u0961\u0971-\u0980\u0985-\u098C\u098F\u0990\u0993-\u09A8\u09AA-\u09B0\u09B2\u09B6-\u09B9\u09BD\u09CE\u09DC\u09DD\u09DF-\u09E1\u09F0\u09F1\u0A05-\u0A0A\u0A0F\u0A10\u0A13-\u0A28\u0A2A-\u0A30\u0A32\u0A33\u0A35\u0A36\u0A38\u0A39\u0A59-\u0A5C\u0A5E\u0A72-\u0A74\u0A85-\u0A8D\u0A8F-\u0A91\u0A93-\u0AA8\u0AAA-\u0AB0\u0AB2\u0AB3\u0AB5-\u0AB9\u0ABD\u0AD0\u0AE0\u0AE1\u0AF9\u0B05-\u0B0C\u0B0F\u0B10\u0B13-\u0B28\u0B2A-\u0B30\u0B32\u0B33\u0B35-\u0B39\u0B3D\u0B5C\u0B5D\u0B5F-\u0B61\u0B71\u0B83\u0B85-\u0B8A\u0B8E-\u0B90\u0B92-\u0B95\u0B99\u0B9A\u0B9C\u0B9E\u0B9F\u0BA3\u0BA4\u0BA8-\u0BAA\u0BAE-\u0BB9\u0BD0\u0C05-\u0C0C\u0C0E-\u0C10\u0C12-\u0C28\u0C2A-\u0C39\u0C3D\u0C58-\u0C5A\u0C60\u0C61\u0C80\u0C85-\u0C8C\u0C8E-\u0C90\u0C92-\u0CA8\u0CAA-\u0CB3\u0CB5-\u0CB9\u0CBD\u0CDE\u0CE0\u0CE1\u0CF1\u0CF2\u0D05-\u0D0C\u0D0E-\u0D10\u0D12-\u0D3A\u0D3D\u0D4E\u0D54-\u0D56\u0D5F-\u0D61\u0D7A-\u0D7F\u0D85-\u0D96\u0D9A-\u0DB1\u0DB3-\u0DBB\u0DBD\u0DC0-\u0DC6\u0E01-\u0E30\u0E32\u0E33\u0E40-\u0E46\u0E81\u0E82\u0E84\u0E87\u0E88\u0E8A\u0E8D\u0E94-\u0E97\u0E99-\u0E9F\u0EA1-\u0EA3\u0EA5\u0EA7\u0EAA\u0EAB\u0EAD-\u0EB0\u0EB2\u0EB3\u0EBD\u0EC0-\u0EC4\u0EC6\u0EDC-\u0EDF\u0F00\u0F40-\u0F47\u0F49-\u0F6C\u0F88-\u0F8C\u1000-\u102A\u103F\u1050-\u1055\u105A-\u105D\u1061\u1065\u1066\u106E-\u1070\u1075-\u1081\u108E\u10A0-\u10C5\u10C7\u10CD\u10D0-\u10FA\u10FC-\u1248\u124A-\u124D\u1250-\u1256\u1258\u125A-\u125D\u1260-\u1288\u128A-\u128D\u1290-\u12B0\u12B2-\u12B5\u12B8-\u12BE\u12C0\u12C2-\u12C5\u12C8-\u12D6\u12D8-\u1310\u1312-\u1315\u1318-\u135A\u1380-\u138F\u13A0-\u13F5\u13F8-\u13FD\u1401-\u166C\u166F-\u167F\u1681-\u169A\u16A0-\u16EA\u16EE-\u16F8\u1700-\u170C\u170E-\u1711\u1720-\u1731\u1740-\u1751\u1760-\u176C\u176E-\u1770\u1780-\u17B3\u17D7\u17DC\u1820-\u1877\u1880-\u1884\u1887-\u18A8\u18AA\u18B0-\u18F5\u1900-\u191E\u1950-\u196D\u1970-\u1974\u1980-\u19AB\u19B0-\u19C9\u1A00-\u1A16\u1A20-\u1A54\u1AA7\u1B05-\u1B33\u1B45-\u1B4B\u1B83-\u1BA0\u1BAE\u1BAF\u1BBA-\u1BE5\u1C00-\u1C23\u1C4D-\u1C4F\u1C5A-\u1C7D\u1C80-\u1C88\u1CE9-\u1CEC\u1CEE-\u1CF1\u1CF5\u1CF6\u1D00-\u1DBF\u1E00-\u1F15\u1F18-\u1F1D\u1F20-\u1F45\u1F48-\u1F4D\u1F50-\u1F57\u1F59\u1F5B\u1F5D\u1F5F-\u1F7D\u1F80-\u1FB4\u1FB6-\u1FBC\u1FBE\u1FC2-\u1FC4\u1FC6-\u1FCC\u1FD0-\u1FD3\u1FD6-\u1FDB\u1FE0-\u1FEC\u1FF2-\u1FF4\u1FF6-\u1FFC\u2071\u207F\u2090-\u209C\u2102\u2107\u210A-\u2113\u2115\u2119-\u211D\u2124\u2126\u2128\u212A-\u212D\u212F-\u2139\u213C-\u213F\u2145-\u2149\u214E\u2160-\u2188\u2C00-\u2C2E\u2C30-\u2C5E\u2C60-\u2CE4\u2CEB-\u2CEE\u2CF2\u2CF3\u2D00-\u2D25\u2D27\u2D2D\u2D30-\u2D67\u2D6F\u2D80-\u2D96\u2DA0-\u2DA6\u2DA8-\u2DAE\u2DB0-\u2DB6\u2DB8-\u2DBE\u2DC0-\u2DC6\u2DC8-\u2DCE\u2DD0-\u2DD6\u2DD8-\u2DDE\u2E2F\u3005-\u3007\u3021-\u3029\u3031-\u3035\u3038-\u303C\u3041-\u3096\u309D-\u309F\u30A1-\u30FA\u30FC-\u30FF\u3105-\u312D\u3131-\u318E\u31A0-\u31BA\u31F0-\u31FF\u3400-\u4DB5\u4E00-\u9FD5\uA000-\uA48C\uA4D0-\uA4FD\uA500-\uA60C\uA610-\uA61F\uA62A\uA62B\uA640-\uA66E\uA67F-\uA69D\uA6A0-\uA6EF\uA717-\uA71F\uA722-\uA788\uA78B-\uA7AE\uA7B0-\uA7B7\uA7F7-\uA801\uA803-\uA805\uA807-\uA80A\uA80C-\uA822\uA840-\uA873\uA882-\uA8B3\uA8F2-\uA8F7\uA8FB\uA8FD\uA90A-\uA925\uA930-\uA946\uA960-\uA97C\uA984-\uA9B2\uA9CF\uA9E0-\uA9E4\uA9E6-\uA9EF\uA9FA-\uA9FE\uAA00-\uAA28\uAA40-\uAA42\uAA44-\uAA4B\uAA60-\uAA76\uAA7A\uAA7E-\uAAAF\uAAB1\uAAB5\uAAB6\uAAB9-\uAABD\uAAC0\uAAC2\uAADB-\uAADD\uAAE0-\uAAEA\uAAF2-\uAAF4\uAB01-\uAB06\uAB09-\uAB0E\uAB11-\uAB16\uAB20-\uAB26\uAB28-\uAB2E\uAB30-\uAB5A\uAB5C-\uAB65\uAB70-\uABE2\uAC00-\uD7A3\uD7B0-\uD7C6\uD7CB-\uD7FB\uF900-\uFA6D\uFA70-\uFAD9\uFB00-\uFB06\uFB13-\uFB17\uFB1D\uFB1F-\uFB28\uFB2A-\uFB36\uFB38-\uFB3C\uFB3E\uFB40\uFB41\uFB43\uFB44\uFB46-\uFBB1\uFBD3-\uFD3D\uFD50-\uFD8F\uFD92-\uFDC7\uFDF0-\uFDFB\uFE70-\uFE74\uFE76-\uFEFC\uFF21-\uFF3A\uFF41-\uFF5A\uFF66-\uFFBE\uFFC2-\uFFC7\uFFCA-\uFFCF\uFFD2-\uFFD7\uFFDA-\uFFDC]/,
-        // ECMAScript 5.1/Unicode v9.0.0 NonAsciiIdentifierPart:
-        NonAsciiIdentifierPart: /[\xAA\xB5\xBA\xC0-\xD6\xD8-\xF6\xF8-\u02C1\u02C6-\u02D1\u02E0-\u02E4\u02EC\u02EE\u0300-\u0374\u0376\u0377\u037A-\u037D\u037F\u0386\u0388-\u038A\u038C\u038E-\u03A1\u03A3-\u03F5\u03F7-\u0481\u0483-\u0487\u048A-\u052F\u0531-\u0556\u0559\u0561-\u0587\u0591-\u05BD\u05BF\u05C1\u05C2\u05C4\u05C5\u05C7\u05D0-\u05EA\u05F0-\u05F2\u0610-\u061A\u0620-\u0669\u066E-\u06D3\u06D5-\u06DC\u06DF-\u06E8\u06EA-\u06FC\u06FF\u0710-\u074A\u074D-\u07B1\u07C0-\u07F5\u07FA\u0800-\u082D\u0840-\u085B\u08A0-\u08B4\u08B6-\u08BD\u08D4-\u08E1\u08E3-\u0963\u0966-\u096F\u0971-\u0983\u0985-\u098C\u098F\u0990\u0993-\u09A8\u09AA-\u09B0\u09B2\u09B6-\u09B9\u09BC-\u09C4\u09C7\u09C8\u09CB-\u09CE\u09D7\u09DC\u09DD\u09DF-\u09E3\u09E6-\u09F1\u0A01-\u0A03\u0A05-\u0A0A\u0A0F\u0A10\u0A13-\u0A28\u0A2A-\u0A30\u0A32\u0A33\u0A35\u0A36\u0A38\u0A39\u0A3C\u0A3E-\u0A42\u0A47\u0A48\u0A4B-\u0A4D\u0A51\u0A59-\u0A5C\u0A5E\u0A66-\u0A75\u0A81-\u0A83\u0A85-\u0A8D\u0A8F-\u0A91\u0A93-\u0AA8\u0AAA-\u0AB0\u0AB2\u0AB3\u0AB5-\u0AB9\u0ABC-\u0AC5\u0AC7-\u0AC9\u0ACB-\u0ACD\u0AD0\u0AE0-\u0AE3\u0AE6-\u0AEF\u0AF9\u0B01-\u0B03\u0B05-\u0B0C\u0B0F\u0B10\u0B13-\u0B28\u0B2A-\u0B30\u0B32\u0B33\u0B35-\u0B39\u0B3C-\u0B44\u0B47\u0B48\u0B4B-\u0B4D\u0B56\u0B57\u0B5C\u0B5D\u0B5F-\u0B63\u0B66-\u0B6F\u0B71\u0B82\u0B83\u0B85-\u0B8A\u0B8E-\u0B90\u0B92-\u0B95\u0B99\u0B9A\u0B9C\u0B9E\u0B9F\u0BA3\u0BA4\u0BA8-\u0BAA\u0BAE-\u0BB9\u0BBE-\u0BC2\u0BC6-\u0BC8\u0BCA-\u0BCD\u0BD0\u0BD7\u0BE6-\u0BEF\u0C00-\u0C03\u0C05-\u0C0C\u0C0E-\u0C10\u0C12-\u0C28\u0C2A-\u0C39\u0C3D-\u0C44\u0C46-\u0C48\u0C4A-\u0C4D\u0C55\u0C56\u0C58-\u0C5A\u0C60-\u0C63\u0C66-\u0C6F\u0C80-\u0C83\u0C85-\u0C8C\u0C8E-\u0C90\u0C92-\u0CA8\u0CAA-\u0CB3\u0CB5-\u0CB9\u0CBC-\u0CC4\u0CC6-\u0CC8\u0CCA-\u0CCD\u0CD5\u0CD6\u0CDE\u0CE0-\u0CE3\u0CE6-\u0CEF\u0CF1\u0CF2\u0D01-\u0D03\u0D05-\u0D0C\u0D0E-\u0D10\u0D12-\u0D3A\u0D3D-\u0D44\u0D46-\u0D48\u0D4A-\u0D4E\u0D54-\u0D57\u0D5F-\u0D63\u0D66-\u0D6F\u0D7A-\u0D7F\u0D82\u0D83\u0D85-\u0D96\u0D9A-\u0DB1\u0DB3-\u0DBB\u0DBD\u0DC0-\u0DC6\u0DCA\u0DCF-\u0DD4\u0DD6\u0DD8-\u0DDF\u0DE6-\u0DEF\u0DF2\u0DF3\u0E01-\u0E3A\u0E40-\u0E4E\u0E50-\u0E59\u0E81\u0E82\u0E84\u0E87\u0E88\u0E8A\u0E8D\u0E94-\u0E97\u0E99-\u0E9F\u0EA1-\u0EA3\u0EA5\u0EA7\u0EAA\u0EAB\u0EAD-\u0EB9\u0EBB-\u0EBD\u0EC0-\u0EC4\u0EC6\u0EC8-\u0ECD\u0ED0-\u0ED9\u0EDC-\u0EDF\u0F00\u0F18\u0F19\u0F20-\u0F29\u0F35\u0F37\u0F39\u0F3E-\u0F47\u0F49-\u0F6C\u0F71-\u0F84\u0F86-\u0F97\u0F99-\u0FBC\u0FC6\u1000-\u1049\u1050-\u109D\u10A0-\u10C5\u10C7\u10CD\u10D0-\u10FA\u10FC-\u1248\u124A-\u124D\u1250-\u1256\u1258\u125A-\u125D\u1260-\u1288\u128A-\u128D\u1290-\u12B0\u12B2-\u12B5\u12B8-\u12BE\u12C0\u12C2-\u12C5\u12C8-\u12D6\u12D8-\u1310\u1312-\u1315\u1318-\u135A\u135D-\u135F\u1380-\u138F\u13A0-\u13F5\u13F8-\u13FD\u1401-\u166C\u166F-\u167F\u1681-\u169A\u16A0-\u16EA\u16EE-\u16F8\u1700-\u170C\u170E-\u1714\u1720-\u1734\u1740-\u1753\u1760-\u176C\u176E-\u1770\u1772\u1773\u1780-\u17D3\u17D7\u17DC\u17DD\u17E0-\u17E9\u180B-\u180D\u1810-\u1819\u1820-\u1877\u1880-\u18AA\u18B0-\u18F5\u1900-\u191E\u1920-\u192B\u1930-\u193B\u1946-\u196D\u1970-\u1974\u1980-\u19AB\u19B0-\u19C9\u19D0-\u19D9\u1A00-\u1A1B\u1A20-\u1A5E\u1A60-\u1A7C\u1A7F-\u1A89\u1A90-\u1A99\u1AA7\u1AB0-\u1ABD\u1B00-\u1B4B\u1B50-\u1B59\u1B6B-\u1B73\u1B80-\u1BF3\u1C00-\u1C37\u1C40-\u1C49\u1C4D-\u1C7D\u1C80-\u1C88\u1CD0-\u1CD2\u1CD4-\u1CF6\u1CF8\u1CF9\u1D00-\u1DF5\u1DFB-\u1F15\u1F18-\u1F1D\u1F20-\u1F45\u1F48-\u1F4D\u1F50-\u1F57\u1F59\u1F5B\u1F5D\u1F5F-\u1F7D\u1F80-\u1FB4\u1FB6-\u1FBC\u1FBE\u1FC2-\u1FC4\u1FC6-\u1FCC\u1FD0-\u1FD3\u1FD6-\u1FDB\u1FE0-\u1FEC\u1FF2-\u1FF4\u1FF6-\u1FFC\u200C\u200D\u203F\u2040\u2054\u2071\u207F\u2090-\u209C\u20D0-\u20DC\u20E1\u20E5-\u20F0\u2102\u2107\u210A-\u2113\u2115\u2119-\u211D\u2124\u2126\u2128\u212A-\u212D\u212F-\u2139\u213C-\u213F\u2145-\u2149\u214E\u2160-\u2188\u2C00-\u2C2E\u2C30-\u2C5E\u2C60-\u2CE4\u2CEB-\u2CF3\u2D00-\u2D25\u2D27\u2D2D\u2D30-\u2D67\u2D6F\u2D7F-\u2D96\u2DA0-\u2DA6\u2DA8-\u2DAE\u2DB0-\u2DB6\u2DB8-\u2DBE\u2DC0-\u2DC6\u2DC8-\u2DCE\u2DD0-\u2DD6\u2DD8-\u2DDE\u2DE0-\u2DFF\u2E2F\u3005-\u3007\u3021-\u302F\u3031-\u3035\u3038-\u303C\u3041-\u3096\u3099\u309A\u309D-\u309F\u30A1-\u30FA\u30FC-\u30FF\u3105-\u312D\u3131-\u318E\u31A0-\u31BA\u31F0-\u31FF\u3400-\u4DB5\u4E00-\u9FD5\uA000-\uA48C\uA4D0-\uA4FD\uA500-\uA60C\uA610-\uA62B\uA640-\uA66F\uA674-\uA67D\uA67F-\uA6F1\uA717-\uA71F\uA722-\uA788\uA78B-\uA7AE\uA7B0-\uA7B7\uA7F7-\uA827\uA840-\uA873\uA880-\uA8C5\uA8D0-\uA8D9\uA8E0-\uA8F7\uA8FB\uA8FD\uA900-\uA92D\uA930-\uA953\uA960-\uA97C\uA980-\uA9C0\uA9CF-\uA9D9\uA9E0-\uA9FE\uAA00-\uAA36\uAA40-\uAA4D\uAA50-\uAA59\uAA60-\uAA76\uAA7A-\uAAC2\uAADB-\uAADD\uAAE0-\uAAEF\uAAF2-\uAAF6\uAB01-\uAB06\uAB09-\uAB0E\uAB11-\uAB16\uAB20-\uAB26\uAB28-\uAB2E\uAB30-\uAB5A\uAB5C-\uAB65\uAB70-\uABEA\uABEC\uABED\uABF0-\uABF9\uAC00-\uD7A3\uD7B0-\uD7C6\uD7CB-\uD7FB\uF900-\uFA6D\uFA70-\uFAD9\uFB00-\uFB06\uFB13-\uFB17\uFB1D-\uFB28\uFB2A-\uFB36\uFB38-\uFB3C\uFB3E\uFB40\uFB41\uFB43\uFB44\uFB46-\uFBB1\uFBD3-\uFD3D\uFD50-\uFD8F\uFD92-\uFDC7\uFDF0-\uFDFB\uFE00-\uFE0F\uFE20-\uFE2F\uFE33\uFE34\uFE4D-\uFE4F\uFE70-\uFE74\uFE76-\uFEFC\uFF10-\uFF19\uFF21-\uFF3A\uFF3F\uFF41-\uFF5A\uFF66-\uFFBE\uFFC2-\uFFC7\uFFCA-\uFFCF\uFFD2-\uFFD7\uFFDA-\uFFDC]/
-    };
-
-    ES6Regex = {
-        // ECMAScript 6/Unicode v9.0.0 NonAsciiIdentifierStart:
-        NonAsciiIdentifierStart: /[\xAA\xB5\xBA\xC0-\xD6\xD8-\xF6\xF8-\u02C1\u02C6-\u02D1\u02E0-\u02E4\u02EC\u02EE\u0370-\u0374\u0376\u0377\u037A-\u037D\u037F\u0386\u0388-\u038A\u038C\u038E-\u03A1\u03A3-\u03F5\u03F7-\u0481\u048A-\u052F\u0531-\u0556\u0559\u0561-\u0587\u05D0-\u05EA\u05F0-\u05F2\u0620-\u064A\u066E\u066F\u0671-\u06D3\u06D5\u06E5\u06E6\u06EE\u06EF\u06FA-\u06FC\u06FF\u0710\u0712-\u072F\u074D-\u07A5\u07B1\u07CA-\u07EA\u07F4\u07F5\u07FA\u0800-\u0815\u081A\u0824\u0828\u0840-\u0858\u08A0-\u08B4\u08B6-\u08BD\u0904-\u0939\u093D\u0950\u0958-\u0961\u0971-\u0980\u0985-\u098C\u098F\u0990\u0993-\u09A8\u09AA-\u09B0\u09B2\u09B6-\u09B9\u09BD\u09CE\u09DC\u09DD\u09DF-\u09E1\u09F0\u09F1\u0A05-\u0A0A\u0A0F\u0A10\u0A13-\u0A28\u0A2A-\u0A30\u0A32\u0A33\u0A35\u0A36\u0A38\u0A39\u0A59-\u0A5C\u0A5E\u0A72-\u0A74\u0A85-\u0A8D\u0A8F-\u0A91\u0A93-\u0AA8\u0AAA-\u0AB0\u0AB2\u0AB3\u0AB5-\u0AB9\u0ABD\u0AD0\u0AE0\u0AE1\u0AF9\u0B05-\u0B0C\u0B0F\u0B10\u0B13-\u0B28\u0B2A-\u0B30\u0B32\u0B33\u0B35-\u0B39\u0B3D\u0B5C\u0B5D\u0B5F-\u0B61\u0B71\u0B83\u0B85-\u0B8A\u0B8E-\u0B90\u0B92-\u0B95\u0B99\u0B9A\u0B9C\u0B9E\u0B9F\u0BA3\u0BA4\u0BA8-\u0BAA\u0BAE-\u0BB9\u0BD0\u0C05-\u0C0C\u0C0E-\u0C10\u0C12-\u0C28\u0C2A-\u0C39\u0C3D\u0C58-\u0C5A\u0C60\u0C61\u0C80\u0C85-\u0C8C\u0C8E-\u0C90\u0C92-\u0CA8\u0CAA-\u0CB3\u0CB5-\u0CB9\u0CBD\u0CDE\u0CE0\u0CE1\u0CF1\u0CF2\u0D05-\u0D0C\u0D0E-\u0D10\u0D12-\u0D3A\u0D3D\u0D4E\u0D54-\u0D56\u0D5F-\u0D61\u0D7A-\u0D7F\u0D85-\u0D96\u0D9A-\u0DB1\u0DB3-\u0DBB\u0DBD\u0DC0-\u0DC6\u0E01-\u0E30\u0E32\u0E33\u0E40-\u0E46\u0E81\u0E82\u0E84\u0E87\u0E88\u0E8A\u0E8D\u0E94-\u0E97\u0E99-\u0E9F\u0EA1-\u0EA3\u0EA5\u0EA7\u0EAA\u0EAB\u0EAD-\u0EB0\u0EB2\u0EB3\u0EBD\u0EC0-\u0EC4\u0EC6\u0EDC-\u0EDF\u0F00\u0F40-\u0F47\u0F49-\u0F6C\u0F88-\u0F8C\u1000-\u102A\u103F\u1050-\u1055\u105A-\u105D\u1061\u1065\u1066\u106E-\u1070\u1075-\u1081\u108E\u10A0-\u10C5\u10C7\u10CD\u10D0-\u10FA\u10FC-\u1248\u124A-\u124D\u1250-\u1256\u1258\u125A-\u125D\u1260-\u1288\u128A-\u128D\u1290-\u12B0\u12B2-\u12B5\u12B8-\u12BE\u12C0\u12C2-\u12C5\u12C8-\u12D6\u12D8-\u1310\u1312-\u1315\u1318-\u135A\u1380-\u138F\u13A0-\u13F5\u13F8-\u13FD\u1401-\u166C\u166F-\u167F\u1681-\u169A\u16A0-\u16EA\u16EE-\u16F8\u1700-\u170C\u170E-\u1711\u1720-\u1731\u1740-\u1751\u1760-\u176C\u176E-\u1770\u1780-\u17B3\u17D7\u17DC\u1820-\u1877\u1880-\u18A8\u18AA\u18B0-\u18F5\u1900-\u191E\u1950-\u196D\u1970-\u1974\u1980-\u19AB\u19B0-\u19C9\u1A00-\u1A16\u1A20-\u1A54\u1AA7\u1B05-\u1B33\u1B45-\u1B4B\u1B83-\u1BA0\u1BAE\u1BAF\u1BBA-\u1BE5\u1C00-\u1C23\u1C4D-\u1C4F\u1C5A-\u1C7D\u1C80-\u1C88\u1CE9-\u1CEC\u1CEE-\u1CF1\u1CF5\u1CF6\u1D00-\u1DBF\u1E00-\u1F15\u1F18-\u1F1D\u1F20-\u1F45\u1F48-\u1F4D\u1F50-\u1F57\u1F59\u1F5B\u1F5D\u1F5F-\u1F7D\u1F80-\u1FB4\u1FB6-\u1FBC\u1FBE\u1FC2-\u1FC4\u1FC6-\u1FCC\u1FD0-\u1FD3\u1FD6-\u1FDB\u1FE0-\u1FEC\u1FF2-\u1FF4\u1FF6-\u1FFC\u2071\u207F\u2090-\u209C\u2102\u2107\u210A-\u2113\u2115\u2118-\u211D\u2124\u2126\u2128\u212A-\u2139\u213C-\u213F\u2145-\u2149\u214E\u2160-\u2188\u2C00-\u2C2E\u2C30-\u2C5E\u2C60-\u2CE4\u2CEB-\u2CEE\u2CF2\u2CF3\u2D00-\u2D25\u2D27\u2D2D\u2D30-\u2D67\u2D6F\u2D80-\u2D96\u2DA0-\u2DA6\u2DA8-\u2DAE\u2DB0-\u2DB6\u2DB8-\u2DBE\u2DC0-\u2DC6\u2DC8-\u2DCE\u2DD0-\u2DD6\u2DD8-\u2DDE\u3005-\u3007\u3021-\u3029\u3031-\u3035\u3038-\u303C\u3041-\u3096\u309B-\u309F\u30A1-\u30FA\u30FC-\u30FF\u3105-\u312D\u3131-\u318E\u31A0-\u31BA\u31F0-\u31FF\u3400-\u4DB5\u4E00-\u9FD5\uA000-\uA48C\uA4D0-\uA4FD\uA500-\uA60C\uA610-\uA61F\uA62A\uA62B\uA640-\uA66E\uA67F-\uA69D\uA6A0-\uA6EF\uA717-\uA71F\uA722-\uA788\uA78B-\uA7AE\uA7B0-\uA7B7\uA7F7-\uA801\uA803-\uA805\uA807-\uA80A\uA80C-\uA822\uA840-\uA873\uA882-\uA8B3\uA8F2-\uA8F7\uA8FB\uA8FD\uA90A-\uA925\uA930-\uA946\uA960-\uA97C\uA984-\uA9B2\uA9CF\uA9E0-\uA9E4\uA9E6-\uA9EF\uA9FA-\uA9FE\uAA00-\uAA28\uAA40-\uAA42\uAA44-\uAA4B\uAA60-\uAA76\uAA7A\uAA7E-\uAAAF\uAAB1\uAAB5\uAAB6\uAAB9-\uAABD\uAAC0\uAAC2\uAADB-\uAADD\uAAE0-\uAAEA\uAAF2-\uAAF4\uAB01-\uAB06\uAB09-\uAB0E\uAB11-\uAB16\uAB20-\uAB26\uAB28-\uAB2E\uAB30-\uAB5A\uAB5C-\uAB65\uAB70-\uABE2\uAC00-\uD7A3\uD7B0-\uD7C6\uD7CB-\uD7FB\uF900-\uFA6D\uFA70-\uFAD9\uFB00-\uFB06\uFB13-\uFB17\uFB1D\uFB1F-\uFB28\uFB2A-\uFB36\uFB38-\uFB3C\uFB3E\uFB40\uFB41\uFB43\uFB44\uFB46-\uFBB1\uFBD3-\uFD3D\uFD50-\uFD8F\uFD92-\uFDC7\uFDF0-\uFDFB\uFE70-\uFE74\uFE76-\uFEFC\uFF21-\uFF3A\uFF41-\uFF5A\uFF66-\uFFBE\uFFC2-\uFFC7\uFFCA-\uFFCF\uFFD2-\uFFD7\uFFDA-\uFFDC]|\uD800[\uDC00-\uDC0B\uDC0D-\uDC26\uDC28-\uDC3A\uDC3C\uDC3D\uDC3F-\uDC4D\uDC50-\uDC5D\uDC80-\uDCFA\uDD40-\uDD74\uDE80-\uDE9C\uDEA0-\uDED0\uDF00-\uDF1F\uDF30-\uDF4A\uDF50-\uDF75\uDF80-\uDF9D\uDFA0-\uDFC3\uDFC8-\uDFCF\uDFD1-\uDFD5]|\uD801[\uDC00-\uDC9D\uDCB0-\uDCD3\uDCD8-\uDCFB\uDD00-\uDD27\uDD30-\uDD63\uDE00-\uDF36\uDF40-\uDF55\uDF60-\uDF67]|\uD802[\uDC00-\uDC05\uDC08\uDC0A-\uDC35\uDC37\uDC38\uDC3C\uDC3F-\uDC55\uDC60-\uDC76\uDC80-\uDC9E\uDCE0-\uDCF2\uDCF4\uDCF5\uDD00-\uDD15\uDD20-\uDD39\uDD80-\uDDB7\uDDBE\uDDBF\uDE00\uDE10-\uDE13\uDE15-\uDE17\uDE19-\uDE33\uDE60-\uDE7C\uDE80-\uDE9C\uDEC0-\uDEC7\uDEC9-\uDEE4\uDF00-\uDF35\uDF40-\uDF55\uDF60-\uDF72\uDF80-\uDF91]|\uD803[\uDC00-\uDC48\uDC80-\uDCB2\uDCC0-\uDCF2]|\uD804[\uDC03-\uDC37\uDC83-\uDCAF\uDCD0-\uDCE8\uDD03-\uDD26\uDD50-\uDD72\uDD76\uDD83-\uDDB2\uDDC1-\uDDC4\uDDDA\uDDDC\uDE00-\uDE11\uDE13-\uDE2B\uDE80-\uDE86\uDE88\uDE8A-\uDE8D\uDE8F-\uDE9D\uDE9F-\uDEA8\uDEB0-\uDEDE\uDF05-\uDF0C\uDF0F\uDF10\uDF13-\uDF28\uDF2A-\uDF30\uDF32\uDF33\uDF35-\uDF39\uDF3D\uDF50\uDF5D-\uDF61]|\uD805[\uDC00-\uDC34\uDC47-\uDC4A\uDC80-\uDCAF\uDCC4\uDCC5\uDCC7\uDD80-\uDDAE\uDDD8-\uDDDB\uDE00-\uDE2F\uDE44\uDE80-\uDEAA\uDF00-\uDF19]|\uD806[\uDCA0-\uDCDF\uDCFF\uDEC0-\uDEF8]|\uD807[\uDC00-\uDC08\uDC0A-\uDC2E\uDC40\uDC72-\uDC8F]|\uD808[\uDC00-\uDF99]|\uD809[\uDC00-\uDC6E\uDC80-\uDD43]|[\uD80C\uD81C-\uD820\uD840-\uD868\uD86A-\uD86C\uD86F-\uD872][\uDC00-\uDFFF]|\uD80D[\uDC00-\uDC2E]|\uD811[\uDC00-\uDE46]|\uD81A[\uDC00-\uDE38\uDE40-\uDE5E\uDED0-\uDEED\uDF00-\uDF2F\uDF40-\uDF43\uDF63-\uDF77\uDF7D-\uDF8F]|\uD81B[\uDF00-\uDF44\uDF50\uDF93-\uDF9F\uDFE0]|\uD821[\uDC00-\uDFEC]|\uD822[\uDC00-\uDEF2]|\uD82C[\uDC00\uDC01]|\uD82F[\uDC00-\uDC6A\uDC70-\uDC7C\uDC80-\uDC88\uDC90-\uDC99]|\uD835[\uDC00-\uDC54\uDC56-\uDC9C\uDC9E\uDC9F\uDCA2\uDCA5\uDCA6\uDCA9-\uDCAC\uDCAE-\uDCB9\uDCBB\uDCBD-\uDCC3\uDCC5-\uDD05\uDD07-\uDD0A\uDD0D-\uDD14\uDD16-\uDD1C\uDD1E-\uDD39\uDD3B-\uDD3E\uDD40-\uDD44\uDD46\uDD4A-\uDD50\uDD52-\uDEA5\uDEA8-\uDEC0\uDEC2-\uDEDA\uDEDC-\uDEFA\uDEFC-\uDF14\uDF16-\uDF34\uDF36-\uDF4E\uDF50-\uDF6E\uDF70-\uDF88\uDF8A-\uDFA8\uDFAA-\uDFC2\uDFC4-\uDFCB]|\uD83A[\uDC00-\uDCC4\uDD00-\uDD43]|\uD83B[\uDE00-\uDE03\uDE05-\uDE1F\uDE21\uDE22\uDE24\uDE27\uDE29-\uDE32\uDE34-\uDE37\uDE39\uDE3B\uDE42\uDE47\uDE49\uDE4B\uDE4D-\uDE4F\uDE51\uDE52\uDE54\uDE57\uDE59\uDE5B\uDE5D\uDE5F\uDE61\uDE62\uDE64\uDE67-\uDE6A\uDE6C-\uDE72\uDE74-\uDE77\uDE79-\uDE7C\uDE7E\uDE80-\uDE89\uDE8B-\uDE9B\uDEA1-\uDEA3\uDEA5-\uDEA9\uDEAB-\uDEBB]|\uD869[\uDC00-\uDED6\uDF00-\uDFFF]|\uD86D[\uDC00-\uDF34\uDF40-\uDFFF]|\uD86E[\uDC00-\uDC1D\uDC20-\uDFFF]|\uD873[\uDC00-\uDEA1]|\uD87E[\uDC00-\uDE1D]/,
-        // ECMAScript 6/Unicode v9.0.0 NonAsciiIdentifierPart:
-        NonAsciiIdentifierPart: /[\xAA\xB5\xB7\xBA\xC0-\xD6\xD8-\xF6\xF8-\u02C1\u02C6-\u02D1\u02E0-\u02E4\u02EC\u02EE\u0300-\u0374\u0376\u0377\u037A-\u037D\u037F\u0386-\u038A\u038C\u038E-\u03A1\u03A3-\u03F5\u03F7-\u0481\u0483-\u0487\u048A-\u052F\u0531-\u0556\u0559\u0561-\u0587\u0591-\u05BD\u05BF\u05C1\u05C2\u05C4\u05C5\u05C7\u05D0-\u05EA\u05F0-\u05F2\u0610-\u061A\u0620-\u0669\u066E-\u06D3\u06D5-\u06DC\u06DF-\u06E8\u06EA-\u06FC\u06FF\u0710-\u074A\u074D-\u07B1\u07C0-\u07F5\u07FA\u0800-\u082D\u0840-\u085B\u08A0-\u08B4\u08B6-\u08BD\u08D4-\u08E1\u08E3-\u0963\u0966-\u096F\u0971-\u0983\u0985-\u098C\u098F\u0990\u0993-\u09A8\u09AA-\u09B0\u09B2\u09B6-\u09B9\u09BC-\u09C4\u09C7\u09C8\u09CB-\u09CE\u09D7\u09DC\u09DD\u09DF-\u09E3\u09E6-\u09F1\u0A01-\u0A03\u0A05-\u0A0A\u0A0F\u0A10\u0A13-\u0A28\u0A2A-\u0A30\u0A32\u0A33\u0A35\u0A36\u0A38\u0A39\u0A3C\u0A3E-\u0A42\u0A47\u0A48\u0A4B-\u0A4D\u0A51\u0A59-\u0A5C\u0A5E\u0A66-\u0A75\u0A81-\u0A83\u0A85-\u0A8D\u0A8F-\u0A91\u0A93-\u0AA8\u0AAA-\u0AB0\u0AB2\u0AB3\u0AB5-\u0AB9\u0ABC-\u0AC5\u0AC7-\u0AC9\u0ACB-\u0ACD\u0AD0\u0AE0-\u0AE3\u0AE6-\u0AEF\u0AF9\u0B01-\u0B03\u0B05-\u0B0C\u0B0F\u0B10\u0B13-\u0B28\u0B2A-\u0B30\u0B32\u0B33\u0B35-\u0B39\u0B3C-\u0B44\u0B47\u0B48\u0B4B-\u0B4D\u0B56\u0B57\u0B5C\u0B5D\u0B5F-\u0B63\u0B66-\u0B6F\u0B71\u0B82\u0B83\u0B85-\u0B8A\u0B8E-\u0B90\u0B92-\u0B95\u0B99\u0B9A\u0B9C\u0B9E\u0B9F\u0BA3\u0BA4\u0BA8-\u0BAA\u0BAE-\u0BB9\u0BBE-\u0BC2\u0BC6-\u0BC8\u0BCA-\u0BCD\u0BD0\u0BD7\u0BE6-\u0BEF\u0C00-\u0C03\u0C05-\u0C0C\u0C0E-\u0C10\u0C12-\u0C28\u0C2A-\u0C39\u0C3D-\u0C44\u0C46-\u0C48\u0C4A-\u0C4D\u0C55\u0C56\u0C58-\u0C5A\u0C60-\u0C63\u0C66-\u0C6F\u0C80-\u0C83\u0C85-\u0C8C\u0C8E-\u0C90\u0C92-\u0CA8\u0CAA-\u0CB3\u0CB5-\u0CB9\u0CBC-\u0CC4\u0CC6-\u0CC8\u0CCA-\u0CCD\u0CD5\u0CD6\u0CDE\u0CE0-\u0CE3\u0CE6-\u0CEF\u0CF1\u0CF2\u0D01-\u0D03\u0D05-\u0D0C\u0D0E-\u0D10\u0D12-\u0D3A\u0D3D-\u0D44\u0D46-\u0D48\u0D4A-\u0D4E\u0D54-\u0D57\u0D5F-\u0D63\u0D66-\u0D6F\u0D7A-\u0D7F\u0D82\u0D83\u0D85-\u0D96\u0D9A-\u0DB1\u0DB3-\u0DBB\u0DBD\u0DC0-\u0DC6\u0DCA\u0DCF-\u0DD4\u0DD6\u0DD8-\u0DDF\u0DE6-\u0DEF\u0DF2\u0DF3\u0E01-\u0E3A\u0E40-\u0E4E\u0E50-\u0E59\u0E81\u0E82\u0E84\u0E87\u0E88\u0E8A\u0E8D\u0E94-\u0E97\u0E99-\u0E9F\u0EA1-\u0EA3\u0EA5\u0EA7\u0EAA\u0EAB\u0EAD-\u0EB9\u0EBB-\u0EBD\u0EC0-\u0EC4\u0EC6\u0EC8-\u0ECD\u0ED0-\u0ED9\u0EDC-\u0EDF\u0F00\u0F18\u0F19\u0F20-\u0F29\u0F35\u0F37\u0F39\u0F3E-\u0F47\u0F49-\u0F6C\u0F71-\u0F84\u0F86-\u0F97\u0F99-\u0FBC\u0FC6\u1000-\u1049\u1050-\u109D\u10A0-\u10C5\u10C7\u10CD\u10D0-\u10FA\u10FC-\u1248\u124A-\u124D\u1250-\u1256\u1258\u125A-\u125D\u1260-\u1288\u128A-\u128D\u1290-\u12B0\u12B2-\u12B5\u12B8-\u12BE\u12C0\u12C2-\u12C5\u12C8-\u12D6\u12D8-\u1310\u1312-\u1315\u1318-\u135A\u135D-\u135F\u1369-\u1371\u1380-\u138F\u13A0-\u13F5\u13F8-\u13FD\u1401-\u166C\u166F-\u167F\u1681-\u169A\u16A0-\u16EA\u16EE-\u16F8\u1700-\u170C\u170E-\u1714\u1720-\u1734\u1740-\u1753\u1760-\u176C\u176E-\u1770\u1772\u1773\u1780-\u17D3\u17D7\u17DC\u17DD\u17E0-\u17E9\u180B-\u180D\u1810-\u1819\u1820-\u1877\u1880-\u18AA\u18B0-\u18F5\u1900-\u191E\u1920-\u192B\u1930-\u193B\u1946-\u196D\u1970-\u1974\u1980-\u19AB\u19B0-\u19C9\u19D0-\u19DA\u1A00-\u1A1B\u1A20-\u1A5E\u1A60-\u1A7C\u1A7F-\u1A89\u1A90-\u1A99\u1AA7\u1AB0-\u1ABD\u1B00-\u1B4B\u1B50-\u1B59\u1B6B-\u1B73\u1B80-\u1BF3\u1C00-\u1C37\u1C40-\u1C49\u1C4D-\u1C7D\u1C80-\u1C88\u1CD0-\u1CD2\u1CD4-\u1CF6\u1CF8\u1CF9\u1D00-\u1DF5\u1DFB-\u1F15\u1F18-\u1F1D\u1F20-\u1F45\u1F48-\u1F4D\u1F50-\u1F57\u1F59\u1F5B\u1F5D\u1F5F-\u1F7D\u1F80-\u1FB4\u1FB6-\u1FBC\u1FBE\u1FC2-\u1FC4\u1FC6-\u1FCC\u1FD0-\u1FD3\u1FD6-\u1FDB\u1FE0-\u1FEC\u1FF2-\u1FF4\u1FF6-\u1FFC\u200C\u200D\u203F\u2040\u2054\u2071\u207F\u2090-\u209C\u20D0-\u20DC\u20E1\u20E5-\u20F0\u2102\u2107\u210A-\u2113\u2115\u2118-\u211D\u2124\u2126\u2128\u212A-\u2139\u213C-\u213F\u2145-\u2149\u214E\u2160-\u2188\u2C00-\u2C2E\u2C30-\u2C5E\u2C60-\u2CE4\u2CEB-\u2CF3\u2D00-\u2D25\u2D27\u2D2D\u2D30-\u2D67\u2D6F\u2D7F-\u2D96\u2DA0-\u2DA6\u2DA8-\u2DAE\u2DB0-\u2DB6\u2DB8-\u2DBE\u2DC0-\u2DC6\u2DC8-\u2DCE\u2DD0-\u2DD6\u2DD8-\u2DDE\u2DE0-\u2DFF\u3005-\u3007\u3021-\u302F\u3031-\u3035\u3038-\u303C\u3041-\u3096\u3099-\u309F\u30A1-\u30FA\u30FC-\u30FF\u3105-\u312D\u3131-\u318E\u31A0-\u31BA\u31F0-\u31FF\u3400-\u4DB5\u4E00-\u9FD5\uA000-\uA48C\uA4D0-\uA4FD\uA500-\uA60C\uA610-\uA62B\uA640-\uA66F\uA674-\uA67D\uA67F-\uA6F1\uA717-\uA71F\uA722-\uA788\uA78B-\uA7AE\uA7B0-\uA7B7\uA7F7-\uA827\uA840-\uA873\uA880-\uA8C5\uA8D0-\uA8D9\uA8E0-\uA8F7\uA8FB\uA8FD\uA900-\uA92D\uA930-\uA953\uA960-\uA97C\uA980-\uA9C0\uA9CF-\uA9D9\uA9E0-\uA9FE\uAA00-\uAA36\uAA40-\uAA4D\uAA50-\uAA59\uAA60-\uAA76\uAA7A-\uAAC2\uAADB-\uAADD\uAAE0-\uAAEF\uAAF2-\uAAF6\uAB01-\uAB06\uAB09-\uAB0E\uAB11-\uAB16\uAB20-\uAB26\uAB28-\uAB2E\uAB30-\uAB5A\uAB5C-\uAB65\uAB70-\uABEA\uABEC\uABED\uABF0-\uABF9\uAC00-\uD7A3\uD7B0-\uD7C6\uD7CB-\uD7FB\uF900-\uFA6D\uFA70-\uFAD9\uFB00-\uFB06\uFB13-\uFB17\uFB1D-\uFB28\uFB2A-\uFB36\uFB38-\uFB3C\uFB3E\uFB40\uFB41\uFB43\uFB44\uFB46-\uFBB1\uFBD3-\uFD3D\uFD50-\uFD8F\uFD92-\uFDC7\uFDF0-\uFDFB\uFE00-\uFE0F\uFE20-\uFE2F\uFE33\uFE34\uFE4D-\uFE4F\uFE70-\uFE74\uFE76-\uFEFC\uFF10-\uFF19\uFF21-\uFF3A\uFF3F\uFF41-\uFF5A\uFF66-\uFFBE\uFFC2-\uFFC7\uFFCA-\uFFCF\uFFD2-\uFFD7\uFFDA-\uFFDC]|\uD800[\uDC00-\uDC0B\uDC0D-\uDC26\uDC28-\uDC3A\uDC3C\uDC3D\uDC3F-\uDC4D\uDC50-\uDC5D\uDC80-\uDCFA\uDD40-\uDD74\uDDFD\uDE80-\uDE9C\uDEA0-\uDED0\uDEE0\uDF00-\uDF1F\uDF30-\uDF4A\uDF50-\uDF7A\uDF80-\uDF9D\uDFA0-\uDFC3\uDFC8-\uDFCF\uDFD1-\uDFD5]|\uD801[\uDC00-\uDC9D\uDCA0-\uDCA9\uDCB0-\uDCD3\uDCD8-\uDCFB\uDD00-\uDD27\uDD30-\uDD63\uDE00-\uDF36\uDF40-\uDF55\uDF60-\uDF67]|\uD802[\uDC00-\uDC05\uDC08\uDC0A-\uDC35\uDC37\uDC38\uDC3C\uDC3F-\uDC55\uDC60-\uDC76\uDC80-\uDC9E\uDCE0-\uDCF2\uDCF4\uDCF5\uDD00-\uDD15\uDD20-\uDD39\uDD80-\uDDB7\uDDBE\uDDBF\uDE00-\uDE03\uDE05\uDE06\uDE0C-\uDE13\uDE15-\uDE17\uDE19-\uDE33\uDE38-\uDE3A\uDE3F\uDE60-\uDE7C\uDE80-\uDE9C\uDEC0-\uDEC7\uDEC9-\uDEE6\uDF00-\uDF35\uDF40-\uDF55\uDF60-\uDF72\uDF80-\uDF91]|\uD803[\uDC00-\uDC48\uDC80-\uDCB2\uDCC0-\uDCF2]|\uD804[\uDC00-\uDC46\uDC66-\uDC6F\uDC7F-\uDCBA\uDCD0-\uDCE8\uDCF0-\uDCF9\uDD00-\uDD34\uDD36-\uDD3F\uDD50-\uDD73\uDD76\uDD80-\uDDC4\uDDCA-\uDDCC\uDDD0-\uDDDA\uDDDC\uDE00-\uDE11\uDE13-\uDE37\uDE3E\uDE80-\uDE86\uDE88\uDE8A-\uDE8D\uDE8F-\uDE9D\uDE9F-\uDEA8\uDEB0-\uDEEA\uDEF0-\uDEF9\uDF00-\uDF03\uDF05-\uDF0C\uDF0F\uDF10\uDF13-\uDF28\uDF2A-\uDF30\uDF32\uDF33\uDF35-\uDF39\uDF3C-\uDF44\uDF47\uDF48\uDF4B-\uDF4D\uDF50\uDF57\uDF5D-\uDF63\uDF66-\uDF6C\uDF70-\uDF74]|\uD805[\uDC00-\uDC4A\uDC50-\uDC59\uDC80-\uDCC5\uDCC7\uDCD0-\uDCD9\uDD80-\uDDB5\uDDB8-\uDDC0\uDDD8-\uDDDD\uDE00-\uDE40\uDE44\uDE50-\uDE59\uDE80-\uDEB7\uDEC0-\uDEC9\uDF00-\uDF19\uDF1D-\uDF2B\uDF30-\uDF39]|\uD806[\uDCA0-\uDCE9\uDCFF\uDEC0-\uDEF8]|\uD807[\uDC00-\uDC08\uDC0A-\uDC36\uDC38-\uDC40\uDC50-\uDC59\uDC72-\uDC8F\uDC92-\uDCA7\uDCA9-\uDCB6]|\uD808[\uDC00-\uDF99]|\uD809[\uDC00-\uDC6E\uDC80-\uDD43]|[\uD80C\uD81C-\uD820\uD840-\uD868\uD86A-\uD86C\uD86F-\uD872][\uDC00-\uDFFF]|\uD80D[\uDC00-\uDC2E]|\uD811[\uDC00-\uDE46]|\uD81A[\uDC00-\uDE38\uDE40-\uDE5E\uDE60-\uDE69\uDED0-\uDEED\uDEF0-\uDEF4\uDF00-\uDF36\uDF40-\uDF43\uDF50-\uDF59\uDF63-\uDF77\uDF7D-\uDF8F]|\uD81B[\uDF00-\uDF44\uDF50-\uDF7E\uDF8F-\uDF9F\uDFE0]|\uD821[\uDC00-\uDFEC]|\uD822[\uDC00-\uDEF2]|\uD82C[\uDC00\uDC01]|\uD82F[\uDC00-\uDC6A\uDC70-\uDC7C\uDC80-\uDC88\uDC90-\uDC99\uDC9D\uDC9E]|\uD834[\uDD65-\uDD69\uDD6D-\uDD72\uDD7B-\uDD82\uDD85-\uDD8B\uDDAA-\uDDAD\uDE42-\uDE44]|\uD835[\uDC00-\uDC54\uDC56-\uDC9C\uDC9E\uDC9F\uDCA2\uDCA5\uDCA6\uDCA9-\uDCAC\uDCAE-\uDCB9\uDCBB\uDCBD-\uDCC3\uDCC5-\uDD05\uDD07-\uDD0A\uDD0D-\uDD14\uDD16-\uDD1C\uDD1E-\uDD39\uDD3B-\uDD3E\uDD40-\uDD44\uDD46\uDD4A-\uDD50\uDD52-\uDEA5\uDEA8-\uDEC0\uDEC2-\uDEDA\uDEDC-\uDEFA\uDEFC-\uDF14\uDF16-\uDF34\uDF36-\uDF4E\uDF50-\uDF6E\uDF70-\uDF88\uDF8A-\uDFA8\uDFAA-\uDFC2\uDFC4-\uDFCB\uDFCE-\uDFFF]|\uD836[\uDE00-\uDE36\uDE3B-\uDE6C\uDE75\uDE84\uDE9B-\uDE9F\uDEA1-\uDEAF]|\uD838[\uDC00-\uDC06\uDC08-\uDC18\uDC1B-\uDC21\uDC23\uDC24\uDC26-\uDC2A]|\uD83A[\uDC00-\uDCC4\uDCD0-\uDCD6\uDD00-\uDD4A\uDD50-\uDD59]|\uD83B[\uDE00-\uDE03\uDE05-\uDE1F\uDE21\uDE22\uDE24\uDE27\uDE29-\uDE32\uDE34-\uDE37\uDE39\uDE3B\uDE42\uDE47\uDE49\uDE4B\uDE4D-\uDE4F\uDE51\uDE52\uDE54\uDE57\uDE59\uDE5B\uDE5D\uDE5F\uDE61\uDE62\uDE64\uDE67-\uDE6A\uDE6C-\uDE72\uDE74-\uDE77\uDE79-\uDE7C\uDE7E\uDE80-\uDE89\uDE8B-\uDE9B\uDEA1-\uDEA3\uDEA5-\uDEA9\uDEAB-\uDEBB]|\uD869[\uDC00-\uDED6\uDF00-\uDFFF]|\uD86D[\uDC00-\uDF34\uDF40-\uDFFF]|\uD86E[\uDC00-\uDC1D\uDC20-\uDFFF]|\uD873[\uDC00-\uDEA1]|\uD87E[\uDC00-\uDE1D]|\uDB40[\uDD00-\uDDEF]/
-    };
-
-    function isDecimalDigit(ch) {
-        return 0x30 <= ch && ch <= 0x39;  // 0..9
-    }
-
-    function isHexDigit(ch) {
-        return 0x30 <= ch && ch <= 0x39 ||  // 0..9
-            0x61 <= ch && ch <= 0x66 ||     // a..f
-            0x41 <= ch && ch <= 0x46;       // A..F
-    }
-
-    function isOctalDigit(ch) {
-        return ch >= 0x30 && ch <= 0x37;  // 0..7
-    }
-
-    // 7.2 White Space
-
-    NON_ASCII_WHITESPACES = [
-        0x1680,
-        0x2000, 0x2001, 0x2002, 0x2003, 0x2004, 0x2005, 0x2006, 0x2007, 0x2008, 0x2009, 0x200A,
-        0x202F, 0x205F,
-        0x3000,
-        0xFEFF
-    ];
-
-    function isWhiteSpace(ch) {
-        return ch === 0x20 || ch === 0x09 || ch === 0x0B || ch === 0x0C || ch === 0xA0 ||
-            ch >= 0x1680 && NON_ASCII_WHITESPACES.indexOf(ch) >= 0;
-    }
-
-    // 7.3 Line Terminators
-
-    function isLineTerminator(ch) {
-        return ch === 0x0A || ch === 0x0D || ch === 0x2028 || ch === 0x2029;
-    }
-
-    // 7.6 Identifier Names and Identifiers
-
-    function fromCodePoint(cp) {
-        if (cp <= 0xFFFF) { return String.fromCharCode(cp); }
-        var cu1 = String.fromCharCode(Math.floor((cp - 0x10000) / 0x400) + 0xD800);
-        var cu2 = String.fromCharCode(((cp - 0x10000) % 0x400) + 0xDC00);
-        return cu1 + cu2;
-    }
-
-    IDENTIFIER_START = new Array(0x80);
-    for(ch = 0; ch < 0x80; ++ch) {
-        IDENTIFIER_START[ch] =
-            ch >= 0x61 && ch <= 0x7A ||  // a..z
-            ch >= 0x41 && ch <= 0x5A ||  // A..Z
-            ch === 0x24 || ch === 0x5F;  // $ (dollar) and _ (underscore)
-    }
-
-    IDENTIFIER_PART = new Array(0x80);
-    for(ch = 0; ch < 0x80; ++ch) {
-        IDENTIFIER_PART[ch] =
-            ch >= 0x61 && ch <= 0x7A ||  // a..z
-            ch >= 0x41 && ch <= 0x5A ||  // A..Z
-            ch >= 0x30 && ch <= 0x39 ||  // 0..9
-            ch === 0x24 || ch === 0x5F;  // $ (dollar) and _ (underscore)
-    }
-
-    function isIdentifierStartES5(ch) {
-        return ch < 0x80 ? IDENTIFIER_START[ch] : ES5Regex.NonAsciiIdentifierStart.test(fromCodePoint(ch));
-    }
-
-    function isIdentifierPartES5(ch) {
-        return ch < 0x80 ? IDENTIFIER_PART[ch] : ES5Regex.NonAsciiIdentifierPart.test(fromCodePoint(ch));
-    }
-
-    function isIdentifierStartES6(ch) {
-        return ch < 0x80 ? IDENTIFIER_START[ch] : ES6Regex.NonAsciiIdentifierStart.test(fromCodePoint(ch));
-    }
-
-    function isIdentifierPartES6(ch) {
-        return ch < 0x80 ? IDENTIFIER_PART[ch] : ES6Regex.NonAsciiIdentifierPart.test(fromCodePoint(ch));
-    }
-
-    module.exports = {
-        isDecimalDigit: isDecimalDigit,
-        isHexDigit: isHexDigit,
-        isOctalDigit: isOctalDigit,
-        isWhiteSpace: isWhiteSpace,
-        isLineTerminator: isLineTerminator,
-        isIdentifierStartES5: isIdentifierStartES5,
-        isIdentifierPartES5: isIdentifierPartES5,
-        isIdentifierStartES6: isIdentifierStartES6,
-        isIdentifierPartES6: isIdentifierPartES6
-    };
-}());
-/* vim: set sw=4 ts=4 et tw=80 : */
diff --git a/package.json b/package.json
index cebdd1b..05c6aff 100644
--- a/package.json
+++ b/package.json
@@ -2,43 +2,74 @@
   "name": "esutils",
   "description": "utility box for ECMAScript language tools",
   "homepage": "https://github.com/estools/esutils",
-  "main": "lib/utils.js",
+  "bugs": "https://github.com/estools/esutils/issues",
+  "main": "./dist/esutils.min.js",
+  "exports": {
+    "import": "./dist/esutils.esm.min.js",
+    "require": "./dist/esutils.min.js"
+  },
   "version": "2.0.4-dev",
   "engines": {
     "node": ">=0.10.0"
   },
   "directories": {
-    "lib": "./lib"
+    "lib": "./dist"
   },
   "files": [
     "LICENSE.BSD",
     "README.md",
-    "lib"
+    "dist"
+  ],
+  "keywords": [
+    "ecmascript"
   ],
-  "maintainers": [
-    {
-      "name": "Yusuke Suzuki",
-      "email": "utatane.tea@gmail.com",
-      "web": "http://github.com/Constellation"
-    }
+  "author": {
+    "name": "Yusuke Suzuki",
+    "email": "utatane.tea@gmail.com",
+    "web": "http://github.com/Constellation"
+  },
+  "contributors": [
+    "Brett Zamir"
   ],
   "repository": {
     "type": "git",
     "url": "http://github.com/estools/esutils.git"
   },
+  "dependencies": {},
   "devDependencies": {
-    "chai": "~1.7.2",
-    "coffee-script": "~1.6.3",
-    "jshint": "2.6.3",
-    "mocha": "~2.2.1",
-    "regenerate": "~1.3.1",
-    "unicode-9.0.0": "~0.7.0"
+    "@babel/core": "^7.17.9",
+    "@babel/preset-env": "^7.16.11",
+    "@babel/register": "^7.17.7",
+    "@rollup/plugin-babel": "^5.3.1",
+    "chai": "~4.3.6",
+    "coffeescript": "^2.6.1",
+    "eslint": "^8.12.0",
+    "mocha": "~9.2.2",
+    "nyc": "^15.1.0",
+    "regenerate": "~1.4.2",
+    "rollup": "^2.70.1",
+    "rollup-plugin-terser": "^7.0.2",
+    "unicode-13.0.0": "^0.8.0"
   },
   "license": "BSD-2-Clause",
+  "nyc": {
+    "branches": 100,
+    "lines": 100,
+    "functions": 100,
+    "statements": 100,
+    "reporter": [
+      "html",
+      "text"
+    ],
+    "exclude": [
+      "test"
+    ]
+  },
   "scripts": {
-    "test": "npm run-script lint && npm run-script unit-test",
-    "lint": "jshint lib/*.js",
-    "unit-test": "mocha --compilers coffee:coffee-script -R spec",
+    "build": "rollup -c",
+    "test": "npm run lint && npm run unit-test",
+    "lint": "eslint .",
+    "unit-test": "nyc mocha --require @babel/register --require chai/register-expect.js --require coffeescript/register.js test/**",
     "generate-regex": "node tools/generate-identifier-regex.js"
   }
 }
diff --git a/rollup.config.js b/rollup.config.js
new file mode 100644
index 0000000..6c348fe
--- /dev/null
+++ b/rollup.config.js
@@ -0,0 +1,45 @@
+import { terser } from 'rollup-plugin-terser';
+
+import babel from '@rollup/plugin-babel';
+
+/**
+ * @external RollupConfig
+ * @type {PlainObject}
+ * @see {@link https://rollupjs.org/guide/en#big-list-of-options}
+ */
+
+/**
+ * @param {PlainObject} [config= {}]
+ * @param {boolean} [config.minifying=false]
+ * @param {string} [config.format='umd']
+ * @returns {external:RollupConfig}
+ */
+function getRollupObject ({ minifying, format = 'umd' } = {}) {
+    const nonMinified = {
+        input: 'src/utils.js',
+        output: {
+            format,
+            sourcemap: minifying,
+            file: `dist/esutils${
+                format === 'umd' ? '' : `.${format}`
+            }${minifying ? '.min' : ''}.js`,
+            name: 'esutils'
+        },
+        plugins: [
+            babel({
+                babelHelpers: 'bundled'
+            })
+        ]
+    };
+    if (minifying) {
+        nonMinified.plugins.push(terser());
+    }
+    return nonMinified;
+}
+
+export default [
+    getRollupObject({ minifying: true, format: 'umd' }),
+    getRollupObject({ minifying: false, format: 'umd' }),
+    getRollupObject({ minifying: true, format: 'esm' }),
+    getRollupObject({ minifying: false, format: 'esm' })
+];
diff --git a/src/ast.js b/src/ast.js
new file mode 100644
index 0000000..59ce678
--- /dev/null
+++ b/src/ast.js
@@ -0,0 +1,139 @@
+/*
+  Copyright (C) 2013 Yusuke Suzuki <utatane.tea@gmail.com>
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in the
+      documentation and/or other materials provided with the distribution.
+
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 'AS IS'
+  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+  ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
+  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+function isExpression(node) {
+    if (node == null) { return false; }
+    switch (node.type) {
+        case 'ArrayExpression':
+        case 'AssignmentExpression':
+        case 'BinaryExpression':
+        case 'CallExpression':
+        case 'ConditionalExpression':
+        case 'FunctionExpression':
+        case 'Identifier':
+        case 'Literal':
+        case 'LogicalExpression':
+        case 'MemberExpression':
+        case 'NewExpression':
+        case 'ObjectExpression':
+        case 'SequenceExpression':
+        case 'ThisExpression':
+        case 'UnaryExpression':
+        case 'UpdateExpression':
+            return true;
+    }
+    return false;
+}
+
+function isIterationStatement(node) {
+    if (node == null) { return false; }
+    switch (node.type) {
+        case 'DoWhileStatement':
+        case 'ForInStatement':
+        case 'ForStatement':
+        case 'WhileStatement':
+            return true;
+    }
+    return false;
+}
+
+function isStatement(node) {
+    if (node == null) { return false; }
+    switch (node.type) {
+        case 'BlockStatement':
+        case 'BreakStatement':
+        case 'ContinueStatement':
+        case 'DebuggerStatement':
+        case 'DoWhileStatement':
+        case 'EmptyStatement':
+        case 'ExpressionStatement':
+        case 'ForInStatement':
+        case 'ForStatement':
+        case 'IfStatement':
+        case 'LabeledStatement':
+        case 'ReturnStatement':
+        case 'SwitchStatement':
+        case 'ThrowStatement':
+        case 'TryStatement':
+        case 'VariableDeclaration':
+        case 'WhileStatement':
+        case 'WithStatement':
+            return true;
+    }
+    return false;
+}
+
+function isSourceElement(node) {
+    return isStatement(node) || node != null && node.type === 'FunctionDeclaration';
+}
+
+function trailingStatement(node) {
+    switch (node.type) {
+        case 'IfStatement':
+            if (node.alternate != null) {
+                return node.alternate;
+            }
+            return node.consequent;
+
+        case 'LabeledStatement':
+        case 'ForStatement':
+        case 'ForInStatement':
+        case 'WhileStatement':
+        case 'WithStatement':
+            return node.body;
+    }
+    return null;
+}
+
+function isProblematicIfStatement(node) {
+    if (node.type !== 'IfStatement') {
+        return false;
+    }
+    if (node.alternate == null) {
+        return false;
+    }
+    let current = node.consequent;
+    do {
+        if (current.type === 'IfStatement') {
+            if (current.alternate == null)  {
+                return true;
+            }
+        }
+        current = trailingStatement(current);
+    } while (current);
+
+    return false;
+}
+
+export {
+    isExpression,
+    isStatement,
+    isIterationStatement,
+    isSourceElement,
+    isProblematicIfStatement,
+
+    trailingStatement
+};
+
+/* vim: set sw=4 ts=4 et tw=80 : */
diff --git a/src/code.js b/src/code.js
new file mode 100644
index 0000000..3bb5b6b
--- /dev/null
+++ b/src/code.js
@@ -0,0 +1,119 @@
+/* eslint-disable no-misleading-character-class */
+/*
+  Copyright (C) 2013-2014 Yusuke Suzuki <utatane.tea@gmail.com>
+  Copyright (C) 2014 Ivan Nikulin <ifaaan@gmail.com>
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in the
+      documentation and/or other materials provided with the distribution.
+
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+  ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
+  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+import * as ES5Regex from './es5-identifier.js';
+import * as ES6Regex from './es6-identifier.js';
+
+function isDecimalDigit(ch) {
+    return 0x30 <= ch && ch <= 0x39;  // 0..9
+}
+
+function isHexDigit(ch) {
+    return 0x30 <= ch && ch <= 0x39 ||  // 0..9
+        0x61 <= ch && ch <= 0x66 ||     // a..f
+        0x41 <= ch && ch <= 0x46;       // A..F
+}
+
+function isOctalDigit(ch) {
+    return ch >= 0x30 && ch <= 0x37;  // 0..7
+}
+
+// 7.2 White Space
+
+const NON_ASCII_WHITESPACES = [
+    0x1680,
+    0x2000, 0x2001, 0x2002, 0x2003, 0x2004, 0x2005, 0x2006, 0x2007, 0x2008, 0x2009, 0x200A,
+    0x202F, 0x205F,
+    0x3000,
+    0xFEFF
+];
+
+function isWhiteSpace(ch) {
+    return ch === 0x20 || ch === 0x09 || ch === 0x0B || ch === 0x0C || ch === 0xA0 ||
+        ch >= 0x1680 && NON_ASCII_WHITESPACES.indexOf(ch) >= 0;
+}
+
+// 7.3 Line Terminators
+
+function isLineTerminator(ch) {
+    return ch === 0x0A || ch === 0x0D || ch === 0x2028 || ch === 0x2029;
+}
+
+// 7.6 Identifier Names and Identifiers
+
+function fromCodePoint(cp) {
+    if (cp <= 0xFFFF) { return String.fromCharCode(cp); }
+    const cu1 = String.fromCharCode(Math.floor((cp - 0x10000) / 0x400) + 0xD800);
+    const cu2 = String.fromCharCode(((cp - 0x10000) % 0x400) + 0xDC00);
+    return cu1 + cu2;
+}
+
+const IDENTIFIER_START = new Array(0x80);
+for(let ch = 0; ch < 0x80; ++ch) {
+    IDENTIFIER_START[ch] =
+        ch >= 0x61 && ch <= 0x7A ||  // a..z
+        ch >= 0x41 && ch <= 0x5A ||  // A..Z
+        ch === 0x24 || ch === 0x5F;  // $ (dollar) and _ (underscore)
+}
+
+const IDENTIFIER_PART = new Array(0x80);
+for(let ch = 0; ch < 0x80; ++ch) {
+    IDENTIFIER_PART[ch] =
+        ch >= 0x61 && ch <= 0x7A ||  // a..z
+        ch >= 0x41 && ch <= 0x5A ||  // A..Z
+        ch >= 0x30 && ch <= 0x39 ||  // 0..9
+        ch === 0x24 || ch === 0x5F;  // $ (dollar) and _ (underscore)
+}
+
+function isIdentifierStartES5(ch) {
+    return ch < 0x80 ? IDENTIFIER_START[ch] : ES5Regex.NonAsciiIdentifierStart.test(fromCodePoint(ch));
+}
+
+function isIdentifierPartES5(ch) {
+    return ch < 0x80 ? IDENTIFIER_PART[ch] : ES5Regex.NonAsciiIdentifierPart.test(fromCodePoint(ch));
+}
+
+function isIdentifierStartES6(ch) {
+    return ch < 0x80 ? IDENTIFIER_START[ch] : ES6Regex.NonAsciiIdentifierStart.test(fromCodePoint(ch));
+}
+
+function isIdentifierPartES6(ch) {
+    return ch < 0x80 ? IDENTIFIER_PART[ch] : ES6Regex.NonAsciiIdentifierPart.test(fromCodePoint(ch));
+}
+
+export {
+    isDecimalDigit,
+    isHexDigit,
+    isOctalDigit,
+    isWhiteSpace,
+    isLineTerminator,
+    isIdentifierStartES5,
+    isIdentifierPartES5,
+    isIdentifierStartES6,
+    isIdentifierPartES6
+};
+
+/* vim: set sw=4 ts=4 et tw=80 : */
diff --git a/src/es5-identifier.js b/src/es5-identifier.js
new file mode 100644
index 0000000..e3145fc
--- /dev/null
+++ b/src/es5-identifier.js
@@ -0,0 +1,9 @@
+// DO NOT EDIT -- File auto-generated from /tools/generate-identifier-regex.js
+
+// ECMAScript 5.1/Unicode v13.0.0 NonAsciiIdentifierStart:
+const NonAsciiIdentifierStart = /[\xAA\xB5\xBA\xC0-\xD6\xD8-\xF6\xF8-\u02C1\u02C6-\u02D1\u02E0-\u02E4\u02EC\u02EE\u0370-\u0374\u0376\u0377\u037A-\u037D\u037F\u0386\u0388-\u038A\u038C\u038E-\u03A1\u03A3-\u03F5\u03F7-\u0481\u048A-\u052F\u0531-\u0556\u0559\u0560-\u0588\u05D0-\u05EA\u05EF-\u05F2\u0620-\u064A\u066E\u066F\u0671-\u06D3\u06D5\u06E5\u06E6\u06EE\u06EF\u06FA-\u06FC\u06FF\u0710\u0712-\u072F\u074D-\u07A5\u07B1\u07CA-\u07EA\u07F4\u07F5\u07FA\u0800-\u0815\u081A\u0824\u0828\u0840-\u0858\u0860-\u086A\u08A0-\u08B4\u08B6-\u08C7\u0904-\u0939\u093D\u0950\u0958-\u0961\u0971-\u0980\u0985-\u098C\u098F\u0990\u0993-\u09A8\u09AA-\u09B0\u09B2\u09B6-\u09B9\u09BD\u09CE\u09DC\u09DD\u09DF-\u09E1\u09F0\u09F1\u09FC\u0A05-\u0A0A\u0A0F\u0A10\u0A13-\u0A28\u0A2A-\u0A30\u0A32\u0A33\u0A35\u0A36\u0A38\u0A39\u0A59-\u0A5C\u0A5E\u0A72-\u0A74\u0A85-\u0A8D\u0A8F-\u0A91\u0A93-\u0AA8\u0AAA-\u0AB0\u0AB2\u0AB3\u0AB5-\u0AB9\u0ABD\u0AD0\u0AE0\u0AE1\u0AF9\u0B05-\u0B0C\u0B0F\u0B10\u0B13-\u0B28\u0B2A-\u0B30\u0B32\u0B33\u0B35-\u0B39\u0B3D\u0B5C\u0B5D\u0B5F-\u0B61\u0B71\u0B83\u0B85-\u0B8A\u0B8E-\u0B90\u0B92-\u0B95\u0B99\u0B9A\u0B9C\u0B9E\u0B9F\u0BA3\u0BA4\u0BA8-\u0BAA\u0BAE-\u0BB9\u0BD0\u0C05-\u0C0C\u0C0E-\u0C10\u0C12-\u0C28\u0C2A-\u0C39\u0C3D\u0C58-\u0C5A\u0C60\u0C61\u0C80\u0C85-\u0C8C\u0C8E-\u0C90\u0C92-\u0CA8\u0CAA-\u0CB3\u0CB5-\u0CB9\u0CBD\u0CDE\u0CE0\u0CE1\u0CF1\u0CF2\u0D04-\u0D0C\u0D0E-\u0D10\u0D12-\u0D3A\u0D3D\u0D4E\u0D54-\u0D56\u0D5F-\u0D61\u0D7A-\u0D7F\u0D85-\u0D96\u0D9A-\u0DB1\u0DB3-\u0DBB\u0DBD\u0DC0-\u0DC6\u0E01-\u0E30\u0E32\u0E33\u0E40-\u0E46\u0E81\u0E82\u0E84\u0E86-\u0E8A\u0E8C-\u0EA3\u0EA5\u0EA7-\u0EB0\u0EB2\u0EB3\u0EBD\u0EC0-\u0EC4\u0EC6\u0EDC-\u0EDF\u0F00\u0F40-\u0F47\u0F49-\u0F6C\u0F88-\u0F8C\u1000-\u102A\u103F\u1050-\u1055\u105A-\u105D\u1061\u1065\u1066\u106E-\u1070\u1075-\u1081\u108E\u10A0-\u10C5\u10C7\u10CD\u10D0-\u10FA\u10FC-\u1248\u124A-\u124D\u1250-\u1256\u1258\u125A-\u125D\u1260-\u1288\u128A-\u128D\u1290-\u12B0\u12B2-\u12B5\u12B8-\u12BE\u12C0\u12C2-\u12C5\u12C8-\u12D6\u12D8-\u1310\u1312-\u1315\u1318-\u135A\u1380-\u138F\u13A0-\u13F5\u13F8-\u13FD\u1401-\u166C\u166F-\u167F\u1681-\u169A\u16A0-\u16EA\u16EE-\u16F8\u1700-\u170C\u170E-\u1711\u1720-\u1731\u1740-\u1751\u1760-\u176C\u176E-\u1770\u1780-\u17B3\u17D7\u17DC\u1820-\u1878\u1880-\u1884\u1887-\u18A8\u18AA\u18B0-\u18F5\u1900-\u191E\u1950-\u196D\u1970-\u1974\u1980-\u19AB\u19B0-\u19C9\u1A00-\u1A16\u1A20-\u1A54\u1AA7\u1B05-\u1B33\u1B45-\u1B4B\u1B83-\u1BA0\u1BAE\u1BAF\u1BBA-\u1BE5\u1C00-\u1C23\u1C4D-\u1C4F\u1C5A-\u1C7D\u1C80-\u1C88\u1C90-\u1CBA\u1CBD-\u1CBF\u1CE9-\u1CEC\u1CEE-\u1CF3\u1CF5\u1CF6\u1CFA\u1D00-\u1DBF\u1E00-\u1F15\u1F18-\u1F1D\u1F20-\u1F45\u1F48-\u1F4D\u1F50-\u1F57\u1F59\u1F5B\u1F5D\u1F5F-\u1F7D\u1F80-\u1FB4\u1FB6-\u1FBC\u1FBE\u1FC2-\u1FC4\u1FC6-\u1FCC\u1FD0-\u1FD3\u1FD6-\u1FDB\u1FE0-\u1FEC\u1FF2-\u1FF4\u1FF6-\u1FFC\u2071\u207F\u2090-\u209C\u2102\u2107\u210A-\u2113\u2115\u2119-\u211D\u2124\u2126\u2128\u212A-\u212D\u212F-\u2139\u213C-\u213F\u2145-\u2149\u214E\u2160-\u2188\u2C00-\u2C2E\u2C30-\u2C5E\u2C60-\u2CE4\u2CEB-\u2CEE\u2CF2\u2CF3\u2D00-\u2D25\u2D27\u2D2D\u2D30-\u2D67\u2D6F\u2D80-\u2D96\u2DA0-\u2DA6\u2DA8-\u2DAE\u2DB0-\u2DB6\u2DB8-\u2DBE\u2DC0-\u2DC6\u2DC8-\u2DCE\u2DD0-\u2DD6\u2DD8-\u2DDE\u2E2F\u3005-\u3007\u3021-\u3029\u3031-\u3035\u3038-\u303C\u3041-\u3096\u309D-\u309F\u30A1-\u30FA\u30FC-\u30FF\u3105-\u312F\u3131-\u318E\u31A0-\u31BF\u31F0-\u31FF\u3400-\u4DBF\u4E00-\u9FFC\uA000-\uA48C\uA4D0-\uA4FD\uA500-\uA60C\uA610-\uA61F\uA62A\uA62B\uA640-\uA66E\uA67F-\uA69D\uA6A0-\uA6EF\uA717-\uA71F\uA722-\uA788\uA78B-\uA7BF\uA7C2-\uA7CA\uA7F5-\uA801\uA803-\uA805\uA807-\uA80A\uA80C-\uA822\uA840-\uA873\uA882-\uA8B3\uA8F2-\uA8F7\uA8FB\uA8FD\uA8FE\uA90A-\uA925\uA930-\uA946\uA960-\uA97C\uA984-\uA9B2\uA9CF\uA9E0-\uA9E4\uA9E6-\uA9EF\uA9FA-\uA9FE\uAA00-\uAA28\uAA40-\uAA42\uAA44-\uAA4B\uAA60-\uAA76\uAA7A\uAA7E-\uAAAF\uAAB1\uAAB5\uAAB6\uAAB9-\uAABD\uAAC0\uAAC2\uAADB-\uAADD\uAAE0-\uAAEA\uAAF2-\uAAF4\uAB01-\uAB06\uAB09-\uAB0E\uAB11-\uAB16\uAB20-\uAB26\uAB28-\uAB2E\uAB30-\uAB5A\uAB5C-\uAB69\uAB70-\uABE2\uAC00-\uD7A3\uD7B0-\uD7C6\uD7CB-\uD7FB\uF900-\uFA6D\uFA70-\uFAD9\uFB00-\uFB06\uFB13-\uFB17\uFB1D\uFB1F-\uFB28\uFB2A-\uFB36\uFB38-\uFB3C\uFB3E\uFB40\uFB41\uFB43\uFB44\uFB46-\uFBB1\uFBD3-\uFD3D\uFD50-\uFD8F\uFD92-\uFDC7\uFDF0-\uFDFB\uFE70-\uFE74\uFE76-\uFEFC\uFF21-\uFF3A\uFF41-\uFF5A\uFF66-\uFFBE\uFFC2-\uFFC7\uFFCA-\uFFCF\uFFD2-\uFFD7\uFFDA-\uFFDC]/;
+
+// ECMAScript 5.1/Unicode v13.0.0 NonAsciiIdentifierPart:
+const NonAsciiIdentifierPart = /[\xAA\xB5\xBA\xC0-\xD6\xD8-\xF6\xF8-\u02C1\u02C6-\u02D1\u02E0-\u02E4\u02EC\u02EE\u0300-\u0374\u0376\u0377\u037A-\u037D\u037F\u0386\u0388-\u038A\u038C\u038E-\u03A1\u03A3-\u03F5\u03F7-\u0481\u0483-\u0487\u048A-\u052F\u0531-\u0556\u0559\u0560-\u0588\u0591-\u05BD\u05BF\u05C1\u05C2\u05C4\u05C5\u05C7\u05D0-\u05EA\u05EF-\u05F2\u0610-\u061A\u0620-\u0669\u066E-\u06D3\u06D5-\u06DC\u06DF-\u06E8\u06EA-\u06FC\u06FF\u0710-\u074A\u074D-\u07B1\u07C0-\u07F5\u07FA\u07FD\u0800-\u082D\u0840-\u085B\u0860-\u086A\u08A0-\u08B4\u08B6-\u08C7\u08D3-\u08E1\u08E3-\u0963\u0966-\u096F\u0971-\u0983\u0985-\u098C\u098F\u0990\u0993-\u09A8\u09AA-\u09B0\u09B2\u09B6-\u09B9\u09BC-\u09C4\u09C7\u09C8\u09CB-\u09CE\u09D7\u09DC\u09DD\u09DF-\u09E3\u09E6-\u09F1\u09FC\u09FE\u0A01-\u0A03\u0A05-\u0A0A\u0A0F\u0A10\u0A13-\u0A28\u0A2A-\u0A30\u0A32\u0A33\u0A35\u0A36\u0A38\u0A39\u0A3C\u0A3E-\u0A42\u0A47\u0A48\u0A4B-\u0A4D\u0A51\u0A59-\u0A5C\u0A5E\u0A66-\u0A75\u0A81-\u0A83\u0A85-\u0A8D\u0A8F-\u0A91\u0A93-\u0AA8\u0AAA-\u0AB0\u0AB2\u0AB3\u0AB5-\u0AB9\u0ABC-\u0AC5\u0AC7-\u0AC9\u0ACB-\u0ACD\u0AD0\u0AE0-\u0AE3\u0AE6-\u0AEF\u0AF9-\u0AFF\u0B01-\u0B03\u0B05-\u0B0C\u0B0F\u0B10\u0B13-\u0B28\u0B2A-\u0B30\u0B32\u0B33\u0B35-\u0B39\u0B3C-\u0B44\u0B47\u0B48\u0B4B-\u0B4D\u0B55-\u0B57\u0B5C\u0B5D\u0B5F-\u0B63\u0B66-\u0B6F\u0B71\u0B82\u0B83\u0B85-\u0B8A\u0B8E-\u0B90\u0B92-\u0B95\u0B99\u0B9A\u0B9C\u0B9E\u0B9F\u0BA3\u0BA4\u0BA8-\u0BAA\u0BAE-\u0BB9\u0BBE-\u0BC2\u0BC6-\u0BC8\u0BCA-\u0BCD\u0BD0\u0BD7\u0BE6-\u0BEF\u0C00-\u0C0C\u0C0E-\u0C10\u0C12-\u0C28\u0C2A-\u0C39\u0C3D-\u0C44\u0C46-\u0C48\u0C4A-\u0C4D\u0C55\u0C56\u0C58-\u0C5A\u0C60-\u0C63\u0C66-\u0C6F\u0C80-\u0C83\u0C85-\u0C8C\u0C8E-\u0C90\u0C92-\u0CA8\u0CAA-\u0CB3\u0CB5-\u0CB9\u0CBC-\u0CC4\u0CC6-\u0CC8\u0CCA-\u0CCD\u0CD5\u0CD6\u0CDE\u0CE0-\u0CE3\u0CE6-\u0CEF\u0CF1\u0CF2\u0D00-\u0D0C\u0D0E-\u0D10\u0D12-\u0D44\u0D46-\u0D48\u0D4A-\u0D4E\u0D54-\u0D57\u0D5F-\u0D63\u0D66-\u0D6F\u0D7A-\u0D7F\u0D81-\u0D83\u0D85-\u0D96\u0D9A-\u0DB1\u0DB3-\u0DBB\u0DBD\u0DC0-\u0DC6\u0DCA\u0DCF-\u0DD4\u0DD6\u0DD8-\u0DDF\u0DE6-\u0DEF\u0DF2\u0DF3\u0E01-\u0E3A\u0E40-\u0E4E\u0E50-\u0E59\u0E81\u0E82\u0E84\u0E86-\u0E8A\u0E8C-\u0EA3\u0EA5\u0EA7-\u0EBD\u0EC0-\u0EC4\u0EC6\u0EC8-\u0ECD\u0ED0-\u0ED9\u0EDC-\u0EDF\u0F00\u0F18\u0F19\u0F20-\u0F29\u0F35\u0F37\u0F39\u0F3E-\u0F47\u0F49-\u0F6C\u0F71-\u0F84\u0F86-\u0F97\u0F99-\u0FBC\u0FC6\u1000-\u1049\u1050-\u109D\u10A0-\u10C5\u10C7\u10CD\u10D0-\u10FA\u10FC-\u1248\u124A-\u124D\u1250-\u1256\u1258\u125A-\u125D\u1260-\u1288\u128A-\u128D\u1290-\u12B0\u12B2-\u12B5\u12B8-\u12BE\u12C0\u12C2-\u12C5\u12C8-\u12D6\u12D8-\u1310\u1312-\u1315\u1318-\u135A\u135D-\u135F\u1380-\u138F\u13A0-\u13F5\u13F8-\u13FD\u1401-\u166C\u166F-\u167F\u1681-\u169A\u16A0-\u16EA\u16EE-\u16F8\u1700-\u170C\u170E-\u1714\u1720-\u1734\u1740-\u1753\u1760-\u176C\u176E-\u1770\u1772\u1773\u1780-\u17D3\u17D7\u17DC\u17DD\u17E0-\u17E9\u180B-\u180D\u1810-\u1819\u1820-\u1878\u1880-\u18AA\u18B0-\u18F5\u1900-\u191E\u1920-\u192B\u1930-\u193B\u1946-\u196D\u1970-\u1974\u1980-\u19AB\u19B0-\u19C9\u19D0-\u19D9\u1A00-\u1A1B\u1A20-\u1A5E\u1A60-\u1A7C\u1A7F-\u1A89\u1A90-\u1A99\u1AA7\u1AB0-\u1ABD\u1ABF\u1AC0\u1B00-\u1B4B\u1B50-\u1B59\u1B6B-\u1B73\u1B80-\u1BF3\u1C00-\u1C37\u1C40-\u1C49\u1C4D-\u1C7D\u1C80-\u1C88\u1C90-\u1CBA\u1CBD-\u1CBF\u1CD0-\u1CD2\u1CD4-\u1CFA\u1D00-\u1DF9\u1DFB-\u1F15\u1F18-\u1F1D\u1F20-\u1F45\u1F48-\u1F4D\u1F50-\u1F57\u1F59\u1F5B\u1F5D\u1F5F-\u1F7D\u1F80-\u1FB4\u1FB6-\u1FBC\u1FBE\u1FC2-\u1FC4\u1FC6-\u1FCC\u1FD0-\u1FD3\u1FD6-\u1FDB\u1FE0-\u1FEC\u1FF2-\u1FF4\u1FF6-\u1FFC\u200C\u200D\u203F\u2040\u2054\u2071\u207F\u2090-\u209C\u20D0-\u20DC\u20E1\u20E5-\u20F0\u2102\u2107\u210A-\u2113\u2115\u2119-\u211D\u2124\u2126\u2128\u212A-\u212D\u212F-\u2139\u213C-\u213F\u2145-\u2149\u214E\u2160-\u2188\u2C00-\u2C2E\u2C30-\u2C5E\u2C60-\u2CE4\u2CEB-\u2CF3\u2D00-\u2D25\u2D27\u2D2D\u2D30-\u2D67\u2D6F\u2D7F-\u2D96\u2DA0-\u2DA6\u2DA8-\u2DAE\u2DB0-\u2DB6\u2DB8-\u2DBE\u2DC0-\u2DC6\u2DC8-\u2DCE\u2DD0-\u2DD6\u2DD8-\u2DDE\u2DE0-\u2DFF\u2E2F\u3005-\u3007\u3021-\u302F\u3031-\u3035\u3038-\u303C\u3041-\u3096\u3099\u309A\u309D-\u309F\u30A1-\u30FA\u30FC-\u30FF\u3105-\u312F\u3131-\u318E\u31A0-\u31BF\u31F0-\u31FF\u3400-\u4DBF\u4E00-\u9FFC\uA000-\uA48C\uA4D0-\uA4FD\uA500-\uA60C\uA610-\uA62B\uA640-\uA66F\uA674-\uA67D\uA67F-\uA6F1\uA717-\uA71F\uA722-\uA788\uA78B-\uA7BF\uA7C2-\uA7CA\uA7F5-\uA827\uA82C\uA840-\uA873\uA880-\uA8C5\uA8D0-\uA8D9\uA8E0-\uA8F7\uA8FB\uA8FD-\uA92D\uA930-\uA953\uA960-\uA97C\uA980-\uA9C0\uA9CF-\uA9D9\uA9E0-\uA9FE\uAA00-\uAA36\uAA40-\uAA4D\uAA50-\uAA59\uAA60-\uAA76\uAA7A-\uAAC2\uAADB-\uAADD\uAAE0-\uAAEF\uAAF2-\uAAF6\uAB01-\uAB06\uAB09-\uAB0E\uAB11-\uAB16\uAB20-\uAB26\uAB28-\uAB2E\uAB30-\uAB5A\uAB5C-\uAB69\uAB70-\uABEA\uABEC\uABED\uABF0-\uABF9\uAC00-\uD7A3\uD7B0-\uD7C6\uD7CB-\uD7FB\uF900-\uFA6D\uFA70-\uFAD9\uFB00-\uFB06\uFB13-\uFB17\uFB1D-\uFB28\uFB2A-\uFB36\uFB38-\uFB3C\uFB3E\uFB40\uFB41\uFB43\uFB44\uFB46-\uFBB1\uFBD3-\uFD3D\uFD50-\uFD8F\uFD92-\uFDC7\uFDF0-\uFDFB\uFE00-\uFE0F\uFE20-\uFE2F\uFE33\uFE34\uFE4D-\uFE4F\uFE70-\uFE74\uFE76-\uFEFC\uFF10-\uFF19\uFF21-\uFF3A\uFF3F\uFF41-\uFF5A\uFF66-\uFFBE\uFFC2-\uFFC7\uFFCA-\uFFCF\uFFD2-\uFFD7\uFFDA-\uFFDC]/;
+
+export { NonAsciiIdentifierStart, NonAsciiIdentifierPart };
diff --git a/src/es6-identifier.js b/src/es6-identifier.js
new file mode 100644
index 0000000..777eb82
--- /dev/null
+++ b/src/es6-identifier.js
@@ -0,0 +1,9 @@
+// DO NOT EDIT -- File auto-generated from /tools/generate-identifier-regex.js
+
+// ECMAScript 6/Unicode v13.0.0 NonAsciiIdentifierStart:
+const NonAsciiIdentifierStart = /[\xAA\xB5\xBA\xC0-\xD6\xD8-\xF6\xF8-\u02C1\u02C6-\u02D1\u02E0-\u02E4\u02EC\u02EE\u0370-\u0374\u0376\u0377\u037A-\u037D\u037F\u0386\u0388-\u038A\u038C\u038E-\u03A1\u03A3-\u03F5\u03F7-\u0481\u048A-\u052F\u0531-\u0556\u0559\u0560-\u0588\u05D0-\u05EA\u05EF-\u05F2\u0620-\u064A\u066E\u066F\u0671-\u06D3\u06D5\u06E5\u06E6\u06EE\u06EF\u06FA-\u06FC\u06FF\u0710\u0712-\u072F\u074D-\u07A5\u07B1\u07CA-\u07EA\u07F4\u07F5\u07FA\u0800-\u0815\u081A\u0824\u0828\u0840-\u0858\u0860-\u086A\u08A0-\u08B4\u08B6-\u08C7\u0904-\u0939\u093D\u0950\u0958-\u0961\u0971-\u0980\u0985-\u098C\u098F\u0990\u0993-\u09A8\u09AA-\u09B0\u09B2\u09B6-\u09B9\u09BD\u09CE\u09DC\u09DD\u09DF-\u09E1\u09F0\u09F1\u09FC\u0A05-\u0A0A\u0A0F\u0A10\u0A13-\u0A28\u0A2A-\u0A30\u0A32\u0A33\u0A35\u0A36\u0A38\u0A39\u0A59-\u0A5C\u0A5E\u0A72-\u0A74\u0A85-\u0A8D\u0A8F-\u0A91\u0A93-\u0AA8\u0AAA-\u0AB0\u0AB2\u0AB3\u0AB5-\u0AB9\u0ABD\u0AD0\u0AE0\u0AE1\u0AF9\u0B05-\u0B0C\u0B0F\u0B10\u0B13-\u0B28\u0B2A-\u0B30\u0B32\u0B33\u0B35-\u0B39\u0B3D\u0B5C\u0B5D\u0B5F-\u0B61\u0B71\u0B83\u0B85-\u0B8A\u0B8E-\u0B90\u0B92-\u0B95\u0B99\u0B9A\u0B9C\u0B9E\u0B9F\u0BA3\u0BA4\u0BA8-\u0BAA\u0BAE-\u0BB9\u0BD0\u0C05-\u0C0C\u0C0E-\u0C10\u0C12-\u0C28\u0C2A-\u0C39\u0C3D\u0C58-\u0C5A\u0C60\u0C61\u0C80\u0C85-\u0C8C\u0C8E-\u0C90\u0C92-\u0CA8\u0CAA-\u0CB3\u0CB5-\u0CB9\u0CBD\u0CDE\u0CE0\u0CE1\u0CF1\u0CF2\u0D04-\u0D0C\u0D0E-\u0D10\u0D12-\u0D3A\u0D3D\u0D4E\u0D54-\u0D56\u0D5F-\u0D61\u0D7A-\u0D7F\u0D85-\u0D96\u0D9A-\u0DB1\u0DB3-\u0DBB\u0DBD\u0DC0-\u0DC6\u0E01-\u0E30\u0E32\u0E33\u0E40-\u0E46\u0E81\u0E82\u0E84\u0E86-\u0E8A\u0E8C-\u0EA3\u0EA5\u0EA7-\u0EB0\u0EB2\u0EB3\u0EBD\u0EC0-\u0EC4\u0EC6\u0EDC-\u0EDF\u0F00\u0F40-\u0F47\u0F49-\u0F6C\u0F88-\u0F8C\u1000-\u102A\u103F\u1050-\u1055\u105A-\u105D\u1061\u1065\u1066\u106E-\u1070\u1075-\u1081\u108E\u10A0-\u10C5\u10C7\u10CD\u10D0-\u10FA\u10FC-\u1248\u124A-\u124D\u1250-\u1256\u1258\u125A-\u125D\u1260-\u1288\u128A-\u128D\u1290-\u12B0\u12B2-\u12B5\u12B8-\u12BE\u12C0\u12C2-\u12C5\u12C8-\u12D6\u12D8-\u1310\u1312-\u1315\u1318-\u135A\u1380-\u138F\u13A0-\u13F5\u13F8-\u13FD\u1401-\u166C\u166F-\u167F\u1681-\u169A\u16A0-\u16EA\u16EE-\u16F8\u1700-\u170C\u170E-\u1711\u1720-\u1731\u1740-\u1751\u1760-\u176C\u176E-\u1770\u1780-\u17B3\u17D7\u17DC\u1820-\u1878\u1880-\u18A8\u18AA\u18B0-\u18F5\u1900-\u191E\u1950-\u196D\u1970-\u1974\u1980-\u19AB\u19B0-\u19C9\u1A00-\u1A16\u1A20-\u1A54\u1AA7\u1B05-\u1B33\u1B45-\u1B4B\u1B83-\u1BA0\u1BAE\u1BAF\u1BBA-\u1BE5\u1C00-\u1C23\u1C4D-\u1C4F\u1C5A-\u1C7D\u1C80-\u1C88\u1C90-\u1CBA\u1CBD-\u1CBF\u1CE9-\u1CEC\u1CEE-\u1CF3\u1CF5\u1CF6\u1CFA\u1D00-\u1DBF\u1E00-\u1F15\u1F18-\u1F1D\u1F20-\u1F45\u1F48-\u1F4D\u1F50-\u1F57\u1F59\u1F5B\u1F5D\u1F5F-\u1F7D\u1F80-\u1FB4\u1FB6-\u1FBC\u1FBE\u1FC2-\u1FC4\u1FC6-\u1FCC\u1FD0-\u1FD3\u1FD6-\u1FDB\u1FE0-\u1FEC\u1FF2-\u1FF4\u1FF6-\u1FFC\u2071\u207F\u2090-\u209C\u2102\u2107\u210A-\u2113\u2115\u2118-\u211D\u2124\u2126\u2128\u212A-\u2139\u213C-\u213F\u2145-\u2149\u214E\u2160-\u2188\u2C00-\u2C2E\u2C30-\u2C5E\u2C60-\u2CE4\u2CEB-\u2CEE\u2CF2\u2CF3\u2D00-\u2D25\u2D27\u2D2D\u2D30-\u2D67\u2D6F\u2D80-\u2D96\u2DA0-\u2DA6\u2DA8-\u2DAE\u2DB0-\u2DB6\u2DB8-\u2DBE\u2DC0-\u2DC6\u2DC8-\u2DCE\u2DD0-\u2DD6\u2DD8-\u2DDE\u3005-\u3007\u3021-\u3029\u3031-\u3035\u3038-\u303C\u3041-\u3096\u309B-\u309F\u30A1-\u30FA\u30FC-\u30FF\u3105-\u312F\u3131-\u318E\u31A0-\u31BF\u31F0-\u31FF\u3400-\u4DBF\u4E00-\u9FFC\uA000-\uA48C\uA4D0-\uA4FD\uA500-\uA60C\uA610-\uA61F\uA62A\uA62B\uA640-\uA66E\uA67F-\uA69D\uA6A0-\uA6EF\uA717-\uA71F\uA722-\uA788\uA78B-\uA7BF\uA7C2-\uA7CA\uA7F5-\uA801\uA803-\uA805\uA807-\uA80A\uA80C-\uA822\uA840-\uA873\uA882-\uA8B3\uA8F2-\uA8F7\uA8FB\uA8FD\uA8FE\uA90A-\uA925\uA930-\uA946\uA960-\uA97C\uA984-\uA9B2\uA9CF\uA9E0-\uA9E4\uA9E6-\uA9EF\uA9FA-\uA9FE\uAA00-\uAA28\uAA40-\uAA42\uAA44-\uAA4B\uAA60-\uAA76\uAA7A\uAA7E-\uAAAF\uAAB1\uAAB5\uAAB6\uAAB9-\uAABD\uAAC0\uAAC2\uAADB-\uAADD\uAAE0-\uAAEA\uAAF2-\uAAF4\uAB01-\uAB06\uAB09-\uAB0E\uAB11-\uAB16\uAB20-\uAB26\uAB28-\uAB2E\uAB30-\uAB5A\uAB5C-\uAB69\uAB70-\uABE2\uAC00-\uD7A3\uD7B0-\uD7C6\uD7CB-\uD7FB\uF900-\uFA6D\uFA70-\uFAD9\uFB00-\uFB06\uFB13-\uFB17\uFB1D\uFB1F-\uFB28\uFB2A-\uFB36\uFB38-\uFB3C\uFB3E\uFB40\uFB41\uFB43\uFB44\uFB46-\uFBB1\uFBD3-\uFD3D\uFD50-\uFD8F\uFD92-\uFDC7\uFDF0-\uFDFB\uFE70-\uFE74\uFE76-\uFEFC\uFF21-\uFF3A\uFF41-\uFF5A\uFF66-\uFFBE\uFFC2-\uFFC7\uFFCA-\uFFCF\uFFD2-\uFFD7\uFFDA-\uFFDC]|\uD800[\uDC00-\uDC0B\uDC0D-\uDC26\uDC28-\uDC3A\uDC3C\uDC3D\uDC3F-\uDC4D\uDC50-\uDC5D\uDC80-\uDCFA\uDD40-\uDD74\uDE80-\uDE9C\uDEA0-\uDED0\uDF00-\uDF1F\uDF2D-\uDF4A\uDF50-\uDF75\uDF80-\uDF9D\uDFA0-\uDFC3\uDFC8-\uDFCF\uDFD1-\uDFD5]|\uD801[\uDC00-\uDC9D\uDCB0-\uDCD3\uDCD8-\uDCFB\uDD00-\uDD27\uDD30-\uDD63\uDE00-\uDF36\uDF40-\uDF55\uDF60-\uDF67]|\uD802[\uDC00-\uDC05\uDC08\uDC0A-\uDC35\uDC37\uDC38\uDC3C\uDC3F-\uDC55\uDC60-\uDC76\uDC80-\uDC9E\uDCE0-\uDCF2\uDCF4\uDCF5\uDD00-\uDD15\uDD20-\uDD39\uDD80-\uDDB7\uDDBE\uDDBF\uDE00\uDE10-\uDE13\uDE15-\uDE17\uDE19-\uDE35\uDE60-\uDE7C\uDE80-\uDE9C\uDEC0-\uDEC7\uDEC9-\uDEE4\uDF00-\uDF35\uDF40-\uDF55\uDF60-\uDF72\uDF80-\uDF91]|\uD803[\uDC00-\uDC48\uDC80-\uDCB2\uDCC0-\uDCF2\uDD00-\uDD23\uDE80-\uDEA9\uDEB0\uDEB1\uDF00-\uDF1C\uDF27\uDF30-\uDF45\uDFB0-\uDFC4\uDFE0-\uDFF6]|\uD804[\uDC03-\uDC37\uDC83-\uDCAF\uDCD0-\uDCE8\uDD03-\uDD26\uDD44\uDD47\uDD50-\uDD72\uDD76\uDD83-\uDDB2\uDDC1-\uDDC4\uDDDA\uDDDC\uDE00-\uDE11\uDE13-\uDE2B\uDE80-\uDE86\uDE88\uDE8A-\uDE8D\uDE8F-\uDE9D\uDE9F-\uDEA8\uDEB0-\uDEDE\uDF05-\uDF0C\uDF0F\uDF10\uDF13-\uDF28\uDF2A-\uDF30\uDF32\uDF33\uDF35-\uDF39\uDF3D\uDF50\uDF5D-\uDF61]|\uD805[\uDC00-\uDC34\uDC47-\uDC4A\uDC5F-\uDC61\uDC80-\uDCAF\uDCC4\uDCC5\uDCC7\uDD80-\uDDAE\uDDD8-\uDDDB\uDE00-\uDE2F\uDE44\uDE80-\uDEAA\uDEB8\uDF00-\uDF1A]|\uD806[\uDC00-\uDC2B\uDCA0-\uDCDF\uDCFF-\uDD06\uDD09\uDD0C-\uDD13\uDD15\uDD16\uDD18-\uDD2F\uDD3F\uDD41\uDDA0-\uDDA7\uDDAA-\uDDD0\uDDE1\uDDE3\uDE00\uDE0B-\uDE32\uDE3A\uDE50\uDE5C-\uDE89\uDE9D\uDEC0-\uDEF8]|\uD807[\uDC00-\uDC08\uDC0A-\uDC2E\uDC40\uDC72-\uDC8F\uDD00-\uDD06\uDD08\uDD09\uDD0B-\uDD30\uDD46\uDD60-\uDD65\uDD67\uDD68\uDD6A-\uDD89\uDD98\uDEE0-\uDEF2\uDFB0]|\uD808[\uDC00-\uDF99]|\uD809[\uDC00-\uDC6E\uDC80-\uDD43]|[\uD80C\uD81C-\uD820\uD822\uD840-\uD868\uD86A-\uD86C\uD86F-\uD872\uD874-\uD879\uD880-\uD883][\uDC00-\uDFFF]|\uD80D[\uDC00-\uDC2E]|\uD811[\uDC00-\uDE46]|\uD81A[\uDC00-\uDE38\uDE40-\uDE5E\uDED0-\uDEED\uDF00-\uDF2F\uDF40-\uDF43\uDF63-\uDF77\uDF7D-\uDF8F]|\uD81B[\uDE40-\uDE7F\uDF00-\uDF4A\uDF50\uDF93-\uDF9F\uDFE0\uDFE1\uDFE3]|\uD821[\uDC00-\uDFF7]|\uD823[\uDC00-\uDCD5\uDD00-\uDD08]|\uD82C[\uDC00-\uDD1E\uDD50-\uDD52\uDD64-\uDD67\uDD70-\uDEFB]|\uD82F[\uDC00-\uDC6A\uDC70-\uDC7C\uDC80-\uDC88\uDC90-\uDC99]|\uD835[\uDC00-\uDC54\uDC56-\uDC9C\uDC9E\uDC9F\uDCA2\uDCA5\uDCA6\uDCA9-\uDCAC\uDCAE-\uDCB9\uDCBB\uDCBD-\uDCC3\uDCC5-\uDD05\uDD07-\uDD0A\uDD0D-\uDD14\uDD16-\uDD1C\uDD1E-\uDD39\uDD3B-\uDD3E\uDD40-\uDD44\uDD46\uDD4A-\uDD50\uDD52-\uDEA5\uDEA8-\uDEC0\uDEC2-\uDEDA\uDEDC-\uDEFA\uDEFC-\uDF14\uDF16-\uDF34\uDF36-\uDF4E\uDF50-\uDF6E\uDF70-\uDF88\uDF8A-\uDFA8\uDFAA-\uDFC2\uDFC4-\uDFCB]|\uD838[\uDD00-\uDD2C\uDD37-\uDD3D\uDD4E\uDEC0-\uDEEB]|\uD83A[\uDC00-\uDCC4\uDD00-\uDD43\uDD4B]|\uD83B[\uDE00-\uDE03\uDE05-\uDE1F\uDE21\uDE22\uDE24\uDE27\uDE29-\uDE32\uDE34-\uDE37\uDE39\uDE3B\uDE42\uDE47\uDE49\uDE4B\uDE4D-\uDE4F\uDE51\uDE52\uDE54\uDE57\uDE59\uDE5B\uDE5D\uDE5F\uDE61\uDE62\uDE64\uDE67-\uDE6A\uDE6C-\uDE72\uDE74-\uDE77\uDE79-\uDE7C\uDE7E\uDE80-\uDE89\uDE8B-\uDE9B\uDEA1-\uDEA3\uDEA5-\uDEA9\uDEAB-\uDEBB]|\uD869[\uDC00-\uDEDD\uDF00-\uDFFF]|\uD86D[\uDC00-\uDF34\uDF40-\uDFFF]|\uD86E[\uDC00-\uDC1D\uDC20-\uDFFF]|\uD873[\uDC00-\uDEA1\uDEB0-\uDFFF]|\uD87A[\uDC00-\uDFE0]|\uD87E[\uDC00-\uDE1D]|\uD884[\uDC00-\uDF4A]/;
+
+// ECMAScript 6/Unicode v13.0.0 NonAsciiIdentifierPart:
+const NonAsciiIdentifierPart = /[\xAA\xB5\xB7\xBA\xC0-\xD6\xD8-\xF6\xF8-\u02C1\u02C6-\u02D1\u02E0-\u02E4\u02EC\u02EE\u0300-\u0374\u0376\u0377\u037A-\u037D\u037F\u0386-\u038A\u038C\u038E-\u03A1\u03A3-\u03F5\u03F7-\u0481\u0483-\u0487\u048A-\u052F\u0531-\u0556\u0559\u0560-\u0588\u0591-\u05BD\u05BF\u05C1\u05C2\u05C4\u05C5\u05C7\u05D0-\u05EA\u05EF-\u05F2\u0610-\u061A\u0620-\u0669\u066E-\u06D3\u06D5-\u06DC\u06DF-\u06E8\u06EA-\u06FC\u06FF\u0710-\u074A\u074D-\u07B1\u07C0-\u07F5\u07FA\u07FD\u0800-\u082D\u0840-\u085B\u0860-\u086A\u08A0-\u08B4\u08B6-\u08C7\u08D3-\u08E1\u08E3-\u0963\u0966-\u096F\u0971-\u0983\u0985-\u098C\u098F\u0990\u0993-\u09A8\u09AA-\u09B0\u09B2\u09B6-\u09B9\u09BC-\u09C4\u09C7\u09C8\u09CB-\u09CE\u09D7\u09DC\u09DD\u09DF-\u09E3\u09E6-\u09F1\u09FC\u09FE\u0A01-\u0A03\u0A05-\u0A0A\u0A0F\u0A10\u0A13-\u0A28\u0A2A-\u0A30\u0A32\u0A33\u0A35\u0A36\u0A38\u0A39\u0A3C\u0A3E-\u0A42\u0A47\u0A48\u0A4B-\u0A4D\u0A51\u0A59-\u0A5C\u0A5E\u0A66-\u0A75\u0A81-\u0A83\u0A85-\u0A8D\u0A8F-\u0A91\u0A93-\u0AA8\u0AAA-\u0AB0\u0AB2\u0AB3\u0AB5-\u0AB9\u0ABC-\u0AC5\u0AC7-\u0AC9\u0ACB-\u0ACD\u0AD0\u0AE0-\u0AE3\u0AE6-\u0AEF\u0AF9-\u0AFF\u0B01-\u0B03\u0B05-\u0B0C\u0B0F\u0B10\u0B13-\u0B28\u0B2A-\u0B30\u0B32\u0B33\u0B35-\u0B39\u0B3C-\u0B44\u0B47\u0B48\u0B4B-\u0B4D\u0B55-\u0B57\u0B5C\u0B5D\u0B5F-\u0B63\u0B66-\u0B6F\u0B71\u0B82\u0B83\u0B85-\u0B8A\u0B8E-\u0B90\u0B92-\u0B95\u0B99\u0B9A\u0B9C\u0B9E\u0B9F\u0BA3\u0BA4\u0BA8-\u0BAA\u0BAE-\u0BB9\u0BBE-\u0BC2\u0BC6-\u0BC8\u0BCA-\u0BCD\u0BD0\u0BD7\u0BE6-\u0BEF\u0C00-\u0C0C\u0C0E-\u0C10\u0C12-\u0C28\u0C2A-\u0C39\u0C3D-\u0C44\u0C46-\u0C48\u0C4A-\u0C4D\u0C55\u0C56\u0C58-\u0C5A\u0C60-\u0C63\u0C66-\u0C6F\u0C80-\u0C83\u0C85-\u0C8C\u0C8E-\u0C90\u0C92-\u0CA8\u0CAA-\u0CB3\u0CB5-\u0CB9\u0CBC-\u0CC4\u0CC6-\u0CC8\u0CCA-\u0CCD\u0CD5\u0CD6\u0CDE\u0CE0-\u0CE3\u0CE6-\u0CEF\u0CF1\u0CF2\u0D00-\u0D0C\u0D0E-\u0D10\u0D12-\u0D44\u0D46-\u0D48\u0D4A-\u0D4E\u0D54-\u0D57\u0D5F-\u0D63\u0D66-\u0D6F\u0D7A-\u0D7F\u0D81-\u0D83\u0D85-\u0D96\u0D9A-\u0DB1\u0DB3-\u0DBB\u0DBD\u0DC0-\u0DC6\u0DCA\u0DCF-\u0DD4\u0DD6\u0DD8-\u0DDF\u0DE6-\u0DEF\u0DF2\u0DF3\u0E01-\u0E3A\u0E40-\u0E4E\u0E50-\u0E59\u0E81\u0E82\u0E84\u0E86-\u0E8A\u0E8C-\u0EA3\u0EA5\u0EA7-\u0EBD\u0EC0-\u0EC4\u0EC6\u0EC8-\u0ECD\u0ED0-\u0ED9\u0EDC-\u0EDF\u0F00\u0F18\u0F19\u0F20-\u0F29\u0F35\u0F37\u0F39\u0F3E-\u0F47\u0F49-\u0F6C\u0F71-\u0F84\u0F86-\u0F97\u0F99-\u0FBC\u0FC6\u1000-\u1049\u1050-\u109D\u10A0-\u10C5\u10C7\u10CD\u10D0-\u10FA\u10FC-\u1248\u124A-\u124D\u1250-\u1256\u1258\u125A-\u125D\u1260-\u1288\u128A-\u128D\u1290-\u12B0\u12B2-\u12B5\u12B8-\u12BE\u12C0\u12C2-\u12C5\u12C8-\u12D6\u12D8-\u1310\u1312-\u1315\u1318-\u135A\u135D-\u135F\u1369-\u1371\u1380-\u138F\u13A0-\u13F5\u13F8-\u13FD\u1401-\u166C\u166F-\u167F\u1681-\u169A\u16A0-\u16EA\u16EE-\u16F8\u1700-\u170C\u170E-\u1714\u1720-\u1734\u1740-\u1753\u1760-\u176C\u176E-\u1770\u1772\u1773\u1780-\u17D3\u17D7\u17DC\u17DD\u17E0-\u17E9\u180B-\u180D\u1810-\u1819\u1820-\u1878\u1880-\u18AA\u18B0-\u18F5\u1900-\u191E\u1920-\u192B\u1930-\u193B\u1946-\u196D\u1970-\u1974\u1980-\u19AB\u19B0-\u19C9\u19D0-\u19DA\u1A00-\u1A1B\u1A20-\u1A5E\u1A60-\u1A7C\u1A7F-\u1A89\u1A90-\u1A99\u1AA7\u1AB0-\u1ABD\u1ABF\u1AC0\u1B00-\u1B4B\u1B50-\u1B59\u1B6B-\u1B73\u1B80-\u1BF3\u1C00-\u1C37\u1C40-\u1C49\u1C4D-\u1C7D\u1C80-\u1C88\u1C90-\u1CBA\u1CBD-\u1CBF\u1CD0-\u1CD2\u1CD4-\u1CFA\u1D00-\u1DF9\u1DFB-\u1F15\u1F18-\u1F1D\u1F20-\u1F45\u1F48-\u1F4D\u1F50-\u1F57\u1F59\u1F5B\u1F5D\u1F5F-\u1F7D\u1F80-\u1FB4\u1FB6-\u1FBC\u1FBE\u1FC2-\u1FC4\u1FC6-\u1FCC\u1FD0-\u1FD3\u1FD6-\u1FDB\u1FE0-\u1FEC\u1FF2-\u1FF4\u1FF6-\u1FFC\u200C\u200D\u203F\u2040\u2054\u2071\u207F\u2090-\u209C\u20D0-\u20DC\u20E1\u20E5-\u20F0\u2102\u2107\u210A-\u2113\u2115\u2118-\u211D\u2124\u2126\u2128\u212A-\u2139\u213C-\u213F\u2145-\u2149\u214E\u2160-\u2188\u2C00-\u2C2E\u2C30-\u2C5E\u2C60-\u2CE4\u2CEB-\u2CF3\u2D00-\u2D25\u2D27\u2D2D\u2D30-\u2D67\u2D6F\u2D7F-\u2D96\u2DA0-\u2DA6\u2DA8-\u2DAE\u2DB0-\u2DB6\u2DB8-\u2DBE\u2DC0-\u2DC6\u2DC8-\u2DCE\u2DD0-\u2DD6\u2DD8-\u2DDE\u2DE0-\u2DFF\u3005-\u3007\u3021-\u302F\u3031-\u3035\u3038-\u303C\u3041-\u3096\u3099-\u309F\u30A1-\u30FA\u30FC-\u30FF\u3105-\u312F\u3131-\u318E\u31A0-\u31BF\u31F0-\u31FF\u3400-\u4DBF\u4E00-\u9FFC\uA000-\uA48C\uA4D0-\uA4FD\uA500-\uA60C\uA610-\uA62B\uA640-\uA66F\uA674-\uA67D\uA67F-\uA6F1\uA717-\uA71F\uA722-\uA788\uA78B-\uA7BF\uA7C2-\uA7CA\uA7F5-\uA827\uA82C\uA840-\uA873\uA880-\uA8C5\uA8D0-\uA8D9\uA8E0-\uA8F7\uA8FB\uA8FD-\uA92D\uA930-\uA953\uA960-\uA97C\uA980-\uA9C0\uA9CF-\uA9D9\uA9E0-\uA9FE\uAA00-\uAA36\uAA40-\uAA4D\uAA50-\uAA59\uAA60-\uAA76\uAA7A-\uAAC2\uAADB-\uAADD\uAAE0-\uAAEF\uAAF2-\uAAF6\uAB01-\uAB06\uAB09-\uAB0E\uAB11-\uAB16\uAB20-\uAB26\uAB28-\uAB2E\uAB30-\uAB5A\uAB5C-\uAB69\uAB70-\uABEA\uABEC\uABED\uABF0-\uABF9\uAC00-\uD7A3\uD7B0-\uD7C6\uD7CB-\uD7FB\uF900-\uFA6D\uFA70-\uFAD9\uFB00-\uFB06\uFB13-\uFB17\uFB1D-\uFB28\uFB2A-\uFB36\uFB38-\uFB3C\uFB3E\uFB40\uFB41\uFB43\uFB44\uFB46-\uFBB1\uFBD3-\uFD3D\uFD50-\uFD8F\uFD92-\uFDC7\uFDF0-\uFDFB\uFE00-\uFE0F\uFE20-\uFE2F\uFE33\uFE34\uFE4D-\uFE4F\uFE70-\uFE74\uFE76-\uFEFC\uFF10-\uFF19\uFF21-\uFF3A\uFF3F\uFF41-\uFF5A\uFF66-\uFFBE\uFFC2-\uFFC7\uFFCA-\uFFCF\uFFD2-\uFFD7\uFFDA-\uFFDC]|\uD800[\uDC00-\uDC0B\uDC0D-\uDC26\uDC28-\uDC3A\uDC3C\uDC3D\uDC3F-\uDC4D\uDC50-\uDC5D\uDC80-\uDCFA\uDD40-\uDD74\uDDFD\uDE80-\uDE9C\uDEA0-\uDED0\uDEE0\uDF00-\uDF1F\uDF2D-\uDF4A\uDF50-\uDF7A\uDF80-\uDF9D\uDFA0-\uDFC3\uDFC8-\uDFCF\uDFD1-\uDFD5]|\uD801[\uDC00-\uDC9D\uDCA0-\uDCA9\uDCB0-\uDCD3\uDCD8-\uDCFB\uDD00-\uDD27\uDD30-\uDD63\uDE00-\uDF36\uDF40-\uDF55\uDF60-\uDF67]|\uD802[\uDC00-\uDC05\uDC08\uDC0A-\uDC35\uDC37\uDC38\uDC3C\uDC3F-\uDC55\uDC60-\uDC76\uDC80-\uDC9E\uDCE0-\uDCF2\uDCF4\uDCF5\uDD00-\uDD15\uDD20-\uDD39\uDD80-\uDDB7\uDDBE\uDDBF\uDE00-\uDE03\uDE05\uDE06\uDE0C-\uDE13\uDE15-\uDE17\uDE19-\uDE35\uDE38-\uDE3A\uDE3F\uDE60-\uDE7C\uDE80-\uDE9C\uDEC0-\uDEC7\uDEC9-\uDEE6\uDF00-\uDF35\uDF40-\uDF55\uDF60-\uDF72\uDF80-\uDF91]|\uD803[\uDC00-\uDC48\uDC80-\uDCB2\uDCC0-\uDCF2\uDD00-\uDD27\uDD30-\uDD39\uDE80-\uDEA9\uDEAB\uDEAC\uDEB0\uDEB1\uDF00-\uDF1C\uDF27\uDF30-\uDF50\uDFB0-\uDFC4\uDFE0-\uDFF6]|\uD804[\uDC00-\uDC46\uDC66-\uDC6F\uDC7F-\uDCBA\uDCD0-\uDCE8\uDCF0-\uDCF9\uDD00-\uDD34\uDD36-\uDD3F\uDD44-\uDD47\uDD50-\uDD73\uDD76\uDD80-\uDDC4\uDDC9-\uDDCC\uDDCE-\uDDDA\uDDDC\uDE00-\uDE11\uDE13-\uDE37\uDE3E\uDE80-\uDE86\uDE88\uDE8A-\uDE8D\uDE8F-\uDE9D\uDE9F-\uDEA8\uDEB0-\uDEEA\uDEF0-\uDEF9\uDF00-\uDF03\uDF05-\uDF0C\uDF0F\uDF10\uDF13-\uDF28\uDF2A-\uDF30\uDF32\uDF33\uDF35-\uDF39\uDF3B-\uDF44\uDF47\uDF48\uDF4B-\uDF4D\uDF50\uDF57\uDF5D-\uDF63\uDF66-\uDF6C\uDF70-\uDF74]|\uD805[\uDC00-\uDC4A\uDC50-\uDC59\uDC5E-\uDC61\uDC80-\uDCC5\uDCC7\uDCD0-\uDCD9\uDD80-\uDDB5\uDDB8-\uDDC0\uDDD8-\uDDDD\uDE00-\uDE40\uDE44\uDE50-\uDE59\uDE80-\uDEB8\uDEC0-\uDEC9\uDF00-\uDF1A\uDF1D-\uDF2B\uDF30-\uDF39]|\uD806[\uDC00-\uDC3A\uDCA0-\uDCE9\uDCFF-\uDD06\uDD09\uDD0C-\uDD13\uDD15\uDD16\uDD18-\uDD35\uDD37\uDD38\uDD3B-\uDD43\uDD50-\uDD59\uDDA0-\uDDA7\uDDAA-\uDDD7\uDDDA-\uDDE1\uDDE3\uDDE4\uDE00-\uDE3E\uDE47\uDE50-\uDE99\uDE9D\uDEC0-\uDEF8]|\uD807[\uDC00-\uDC08\uDC0A-\uDC36\uDC38-\uDC40\uDC50-\uDC59\uDC72-\uDC8F\uDC92-\uDCA7\uDCA9-\uDCB6\uDD00-\uDD06\uDD08\uDD09\uDD0B-\uDD36\uDD3A\uDD3C\uDD3D\uDD3F-\uDD47\uDD50-\uDD59\uDD60-\uDD65\uDD67\uDD68\uDD6A-\uDD8E\uDD90\uDD91\uDD93-\uDD98\uDDA0-\uDDA9\uDEE0-\uDEF6\uDFB0]|\uD808[\uDC00-\uDF99]|\uD809[\uDC00-\uDC6E\uDC80-\uDD43]|[\uD80C\uD81C-\uD820\uD822\uD840-\uD868\uD86A-\uD86C\uD86F-\uD872\uD874-\uD879\uD880-\uD883][\uDC00-\uDFFF]|\uD80D[\uDC00-\uDC2E]|\uD811[\uDC00-\uDE46]|\uD81A[\uDC00-\uDE38\uDE40-\uDE5E\uDE60-\uDE69\uDED0-\uDEED\uDEF0-\uDEF4\uDF00-\uDF36\uDF40-\uDF43\uDF50-\uDF59\uDF63-\uDF77\uDF7D-\uDF8F]|\uD81B[\uDE40-\uDE7F\uDF00-\uDF4A\uDF4F-\uDF87\uDF8F-\uDF9F\uDFE0\uDFE1\uDFE3\uDFE4\uDFF0\uDFF1]|\uD821[\uDC00-\uDFF7]|\uD823[\uDC00-\uDCD5\uDD00-\uDD08]|\uD82C[\uDC00-\uDD1E\uDD50-\uDD52\uDD64-\uDD67\uDD70-\uDEFB]|\uD82F[\uDC00-\uDC6A\uDC70-\uDC7C\uDC80-\uDC88\uDC90-\uDC99\uDC9D\uDC9E]|\uD834[\uDD65-\uDD69\uDD6D-\uDD72\uDD7B-\uDD82\uDD85-\uDD8B\uDDAA-\uDDAD\uDE42-\uDE44]|\uD835[\uDC00-\uDC54\uDC56-\uDC9C\uDC9E\uDC9F\uDCA2\uDCA5\uDCA6\uDCA9-\uDCAC\uDCAE-\uDCB9\uDCBB\uDCBD-\uDCC3\uDCC5-\uDD05\uDD07-\uDD0A\uDD0D-\uDD14\uDD16-\uDD1C\uDD1E-\uDD39\uDD3B-\uDD3E\uDD40-\uDD44\uDD46\uDD4A-\uDD50\uDD52-\uDEA5\uDEA8-\uDEC0\uDEC2-\uDEDA\uDEDC-\uDEFA\uDEFC-\uDF14\uDF16-\uDF34\uDF36-\uDF4E\uDF50-\uDF6E\uDF70-\uDF88\uDF8A-\uDFA8\uDFAA-\uDFC2\uDFC4-\uDFCB\uDFCE-\uDFFF]|\uD836[\uDE00-\uDE36\uDE3B-\uDE6C\uDE75\uDE84\uDE9B-\uDE9F\uDEA1-\uDEAF]|\uD838[\uDC00-\uDC06\uDC08-\uDC18\uDC1B-\uDC21\uDC23\uDC24\uDC26-\uDC2A\uDD00-\uDD2C\uDD30-\uDD3D\uDD40-\uDD49\uDD4E\uDEC0-\uDEF9]|\uD83A[\uDC00-\uDCC4\uDCD0-\uDCD6\uDD00-\uDD4B\uDD50-\uDD59]|\uD83B[\uDE00-\uDE03\uDE05-\uDE1F\uDE21\uDE22\uDE24\uDE27\uDE29-\uDE32\uDE34-\uDE37\uDE39\uDE3B\uDE42\uDE47\uDE49\uDE4B\uDE4D-\uDE4F\uDE51\uDE52\uDE54\uDE57\uDE59\uDE5B\uDE5D\uDE5F\uDE61\uDE62\uDE64\uDE67-\uDE6A\uDE6C-\uDE72\uDE74-\uDE77\uDE79-\uDE7C\uDE7E\uDE80-\uDE89\uDE8B-\uDE9B\uDEA1-\uDEA3\uDEA5-\uDEA9\uDEAB-\uDEBB]|\uD83E[\uDFF0-\uDFF9]|\uD869[\uDC00-\uDEDD\uDF00-\uDFFF]|\uD86D[\uDC00-\uDF34\uDF40-\uDFFF]|\uD86E[\uDC00-\uDC1D\uDC20-\uDFFF]|\uD873[\uDC00-\uDEA1\uDEB0-\uDFFF]|\uD87A[\uDC00-\uDFE0]|\uD87E[\uDC00-\uDE1D]|\uD884[\uDC00-\uDF4A]|\uDB40[\uDD00-\uDDEF]/;
+
+export { NonAsciiIdentifierStart, NonAsciiIdentifierPart };
diff --git a/lib/keyword.js b/src/keyword.js
similarity index 51%
rename from lib/keyword.js
rename to src/keyword.js
index 13c8c6a..8e329c2 100644
--- a/lib/keyword.js
+++ b/src/keyword.js
@@ -22,13 +22,10 @@
   THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
-(function () {
-    'use strict';
+import * as code from './code.js';
 
-    var code = require('./code');
-
-    function isStrictModeReservedWordES6(id) {
-        switch (id) {
+function isStrictModeReservedWordES6(id) {
+    switch (id) {
         case 'implements':
         case 'interface':
         case 'package':
@@ -40,23 +37,15 @@
             return true;
         default:
             return false;
-        }
     }
+}
 
-    function isKeywordES5(id, strict) {
-        // yield should not be treated as keyword under non-strict mode.
-        if (!strict && id === 'yield') {
-            return false;
-        }
-        return isKeywordES6(id, strict);
+function isKeywordES6(id, strict) {
+    if (strict && isStrictModeReservedWordES6(id)) {
+        return true;
     }
 
-    function isKeywordES6(id, strict) {
-        if (strict && isStrictModeReservedWordES6(id)) {
-            return true;
-        }
-
-        switch (id.length) {
+    switch (id.length) {
         case 2:
             return (id === 'if') || (id === 'in') || (id === 'do');
         case 3:
@@ -79,87 +68,91 @@
             return (id === 'instanceof');
         default:
             return false;
-        }
     }
+}
 
-    function isReservedWordES5(id, strict) {
-        return id === 'null' || id === 'true' || id === 'false' || isKeywordES5(id, strict);
+function isKeywordES5(id, strict) {
+    // yield should not be treated as keyword under non-strict mode.
+    if (!strict && id === 'yield') {
+        return false;
     }
+    return isKeywordES6(id, strict);
+}
 
-    function isReservedWordES6(id, strict) {
-        return id === 'null' || id === 'true' || id === 'false' || isKeywordES6(id, strict);
-    }
+function isReservedWordES5(id, strict) {
+    return id === 'null' || id === 'true' || id === 'false' || isKeywordES5(id, strict);
+}
 
-    function isRestrictedWord(id) {
-        return id === 'eval' || id === 'arguments';
-    }
+function isReservedWordES6(id, strict) {
+    return id === 'null' || id === 'true' || id === 'false' || isKeywordES6(id, strict);
+}
 
-    function isIdentifierNameES5(id) {
-        var i, iz, ch;
+function isRestrictedWord(id) {
+    return id === 'eval' || id === 'arguments';
+}
 
-        if (id.length === 0) { return false; }
+function isIdentifierNameES5(id) {
+    if (id.length === 0) { return false; }
 
-        ch = id.charCodeAt(0);
-        if (!code.isIdentifierStartES5(ch)) {
-            return false;
-        }
-
-        for (i = 1, iz = id.length; i < iz; ++i) {
-            ch = id.charCodeAt(i);
-            if (!code.isIdentifierPartES5(ch)) {
-                return false;
-            }
-        }
-        return true;
+    const ch = id.charCodeAt(0);
+    if (!code.isIdentifierStartES5(ch)) {
+        return false;
     }
 
-    function decodeUtf16(lead, trail) {
-        return (lead - 0xD800) * 0x400 + (trail - 0xDC00) + 0x10000;
+    for (let i = 1, iz = id.length; i < iz; ++i) {
+        const ch = id.charCodeAt(i);
+        if (!code.isIdentifierPartES5(ch)) {
+            return false;
+        }
     }
-
-    function isIdentifierNameES6(id) {
-        var i, iz, ch, lowCh, check;
-
-        if (id.length === 0) { return false; }
-
-        check = code.isIdentifierStartES6;
-        for (i = 0, iz = id.length; i < iz; ++i) {
-            ch = id.charCodeAt(i);
-            if (0xD800 <= ch && ch <= 0xDBFF) {
-                ++i;
-                if (i >= iz) { return false; }
-                lowCh = id.charCodeAt(i);
-                if (!(0xDC00 <= lowCh && lowCh <= 0xDFFF)) {
-                    return false;
-                }
-                ch = decodeUtf16(ch, lowCh);
-            }
-            if (!check(ch)) {
+    return true;
+}
+
+function decodeUtf16(lead, trail) {
+    return (lead - 0xD800) * 0x400 + (trail - 0xDC00) + 0x10000;
+}
+
+function isIdentifierNameES6(id) {
+    if (id.length === 0) { return false; }
+
+    let check = code.isIdentifierStartES6;
+    for (let i = 0, iz = id.length; i < iz; ++i) {
+        let ch = id.charCodeAt(i);
+        if (0xD800 <= ch && ch <= 0xDBFF) {
+            ++i;
+            if (i >= iz) { return false; }
+            const lowCh = id.charCodeAt(i);
+            if (!(0xDC00 <= lowCh && lowCh <= 0xDFFF)) {
                 return false;
             }
-            check = code.isIdentifierPartES6;
+            ch = decodeUtf16(ch, lowCh);
         }
-        return true;
-    }
-
-    function isIdentifierES5(id, strict) {
-        return isIdentifierNameES5(id) && !isReservedWordES5(id, strict);
-    }
-
-    function isIdentifierES6(id, strict) {
-        return isIdentifierNameES6(id) && !isReservedWordES6(id, strict);
+        if (!check(ch)) {
+            return false;
+        }
+        check = code.isIdentifierPartES6;
     }
+    return true;
+}
+
+function isIdentifierES5(id, strict) {
+    return isIdentifierNameES5(id) && !isReservedWordES5(id, strict);
+}
+
+function isIdentifierES6(id, strict) {
+    return isIdentifierNameES6(id) && !isReservedWordES6(id, strict);
+}
+
+export {
+    isKeywordES5,
+    isKeywordES6,
+    isReservedWordES5,
+    isReservedWordES6,
+    isRestrictedWord,
+    isIdentifierNameES5,
+    isIdentifierNameES6,
+    isIdentifierES5,
+    isIdentifierES6
+};
 
-    module.exports = {
-        isKeywordES5: isKeywordES5,
-        isKeywordES6: isKeywordES6,
-        isReservedWordES5: isReservedWordES5,
-        isReservedWordES6: isReservedWordES6,
-        isRestrictedWord: isRestrictedWord,
-        isIdentifierNameES5: isIdentifierNameES5,
-        isIdentifierNameES6: isIdentifierNameES6,
-        isIdentifierES5: isIdentifierES5,
-        isIdentifierES6: isIdentifierES6
-    };
-}());
 /* vim: set sw=4 ts=4 et tw=80 : */
diff --git a/lib/utils.js b/src/utils.js
similarity index 80%
rename from lib/utils.js
rename to src/utils.js
index ce18faa..d664ac2 100644
--- a/lib/utils.js
+++ b/src/utils.js
@@ -23,11 +23,17 @@
 */
 
 
-(function () {
-    'use strict';
+import * as ast from './ast.js';
+import * as code from './code.js';
+import * as keyword from './keyword.js';
+
+export { ast, code, keyword };
+
+/*
+// This syntax is shown on MDN, but not recognized by ESLint parser
+export * as ast from './ast.js';
+export * as code from './code.js';
+export * as keyword from './keyword.js';
+*/
 
-    exports.ast = require('./ast');
-    exports.code = require('./code');
-    exports.keyword = require('./keyword');
-}());
 /* vim: set sw=4 ts=4 et tw=80 : */
diff --git a/test/ast.coffee b/test/ast.coffee
deleted file mode 100644
index 021a7cd..0000000
--- a/test/ast.coffee
+++ /dev/null
@@ -1,175 +0,0 @@
-# Copyright (C) 2013 Yusuke Suzuki <utatane.tea@gmail.com>
-#
-# Redistribution and use in source and binary forms, with or without
-# modification, are permitted provided that the following conditions are met:
-#
-#   * Redistributions of source code must retain the above copyright
-#     notice, this list of conditions and the following disclaimer.
-#   * Redistributions in binary form must reproduce the above copyright
-#     notice, this list of conditions and the following disclaimer in the
-#     documentation and/or other materials provided with the distribution.
-#
-# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
-# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
-# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
-# ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
-# DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
-# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
-# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
-# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
-# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-'use strict'
-
-expect = require('chai').expect
-esutils = require '../'
-
-EMPTY = {type: 'EmptyStatement'}
-
-describe 'ast', ->
-    describe 'isExpression', ->
-        it 'returns false if input is not node', ->
-            expect(esutils.ast.isExpression(0)).to.be.false
-            expect(esutils.ast.isExpression(null)).to.be.false
-            expect(esutils.ast.isExpression(undefined)).to.be.false
-            expect(esutils.ast.isExpression({})).to.be.false
-            expect(esutils.ast.isExpression({type: null})).to.be.false
-            expect(esutils.ast.isExpression({type: undefined})).to.be.false
-
-        it 'returns true if provided node is expression', ->
-            expect(esutils.ast.isExpression({type: "ThisExpression"})).to.be.true
-            expect(esutils.ast.isExpression({type: "Literal", value: 0})).to.be.true
-
-        it 'returns false if provided node is not expression', ->
-            expect(esutils.ast.isExpression({type: "ExpressionStatement"})).to.be.false
-            expect(esutils.ast.isExpression({type: "Program"})).to.be.false
-
-
-    describe 'isIterationStatement', ->
-        it 'returns false if input is not node', ->
-            expect(esutils.ast.isIterationStatement(0)).to.be.false
-            expect(esutils.ast.isIterationStatement(null)).to.be.false
-            expect(esutils.ast.isIterationStatement(undefined)).to.be.false
-            expect(esutils.ast.isIterationStatement({})).to.be.false
-            expect(esutils.ast.isIterationStatement({type: null})).to.be.false
-            expect(esutils.ast.isIterationStatement({type: undefined})).to.be.false
-
-        it 'returns true if provided node is iteration statement', ->
-            expect(esutils.ast.isIterationStatement({type: "ForInStatement"})).to.be.true
-            expect(esutils.ast.isIterationStatement({type: "DoWhileStatement"})).to.be.true
-
-        it 'returns false if provided node is not iteration statement', ->
-            expect(esutils.ast.isIterationStatement({type: "ExpressionStatement"})).to.be.false
-            expect(esutils.ast.isIterationStatement({type: "ThisExpression"})).to.be.false
-
-
-    describe 'isStatement', ->
-        it 'returns false if input is not node', ->
-            expect(esutils.ast.isStatement(0)).to.be.false
-            expect(esutils.ast.isStatement(null)).to.be.false
-            expect(esutils.ast.isStatement(undefined)).to.be.false
-            expect(esutils.ast.isStatement({})).to.be.false
-            expect(esutils.ast.isStatement({type: null})).to.be.false
-            expect(esutils.ast.isStatement({type: undefined})).to.be.false
-
-        it 'returns true if provided node is statement', ->
-            expect(esutils.ast.isStatement({type: "ExpressionStatement"})).to.be.true
-            expect(esutils.ast.isStatement({type: "WhileStatement"})).to.be.true
-
-        it 'returns false if provided node is not statement', ->
-            expect(esutils.ast.isStatement({type: "ThisExpression"})).to.be.false
-            expect(esutils.ast.isStatement({type: "FunctionDeclaration"})).to.be.false
-            expect(esutils.ast.isStatement({type: "Program"})).to.be.false
-
-
-    describe 'isSourceElement', ->
-        it 'returns false if input is not node', ->
-            expect(esutils.ast.isSourceElement(0)).to.be.false
-            expect(esutils.ast.isSourceElement(null)).to.be.false
-            expect(esutils.ast.isSourceElement(undefined)).to.be.false
-            expect(esutils.ast.isSourceElement({})).to.be.false
-            expect(esutils.ast.isSourceElement({type: null})).to.be.false
-            expect(esutils.ast.isSourceElement({type: undefined})).to.be.false
-
-        it 'returns true if provided node is source element', ->
-            expect(esutils.ast.isSourceElement({type: "ExpressionStatement"})).to.be.true
-            expect(esutils.ast.isSourceElement({type: "WhileStatement"})).to.be.true
-            expect(esutils.ast.isSourceElement({type: "FunctionDeclaration"})).to.be.true
-
-        it 'returns false if provided node is not source element', ->
-            expect(esutils.ast.isSourceElement({type: "ThisExpression"})).to.be.false
-            expect(esutils.ast.isSourceElement({type: "Program"})).to.be.false
-
-    describe 'trailingStatement', ->
-        it 'returns trailing statement if node has it', ->
-            expect(esutils.ast.trailingStatement({type: 'WhileStatement', body: EMPTY})).to.be.eq EMPTY
-            expect(esutils.ast.trailingStatement({type: 'WithStatement', body: EMPTY})).to.be.eq EMPTY
-            expect(esutils.ast.trailingStatement({type: 'ForStatement', body: EMPTY})).to.be.eq EMPTY
-            expect(esutils.ast.trailingStatement({type: 'ForInStatement', body: EMPTY})).to.be.eq EMPTY
-            expect(esutils.ast.trailingStatement({type: 'IfStatement', consequent: EMPTY})).to.be.eq EMPTY
-            expect(esutils.ast.trailingStatement({type: 'IfStatement', consequent: {type:'EmptyStatement'}, alternate: EMPTY})).to.be.eq EMPTY
-            expect(esutils.ast.trailingStatement({type: 'LabeledStatement', body: EMPTY})).to.be.eq EMPTY
-
-        it 'returns null if node doens\'t have trailing statement', ->
-            expect(esutils.ast.trailingStatement({type: 'DoWhileStatement', body: EMPTY})).to.be.null
-            expect(esutils.ast.trailingStatement({type: 'ReturnStatement' })).to.be.null
-
-    describe 'isProblematicIfStatement', ->
-        it 'returns true if node is problematic if statement', ->
-            expect(esutils.ast.isProblematicIfStatement(
-                type: 'IfStatement'
-                consequent: {
-                    type: 'IfStatement'
-                    consequent: EMPTY
-                }
-                alternate: EMPTY
-            )).to.be.true
-
-            expect(esutils.ast.isProblematicIfStatement(
-                type: 'IfStatement'
-                consequent:
-                    type: 'LabeledStatement'
-                    body:
-                        type: 'IfStatement'
-                        consequent: EMPTY
-                alternate: EMPTY
-            )).to.be.true
-
-            expect(esutils.ast.isProblematicIfStatement(
-                type: 'IfStatement'
-                consequent:
-                    type: 'WithStatement'
-                    body:
-                        type: 'IfStatement'
-                        consequent: EMPTY
-                alternate: EMPTY
-            )).to.be.true
-
-        it 'returns false if node is not problematic if statement', ->
-            expect(esutils.ast.isProblematicIfStatement(
-                type: 'IfStatement'
-                consequent: EMPTY
-                alternate: EMPTY
-            )).to.be.false
-
-            expect(esutils.ast.isProblematicIfStatement(
-                type: 'IfStatement'
-                consequent:
-                    type: 'BlockStatement'
-                    body: [
-                        type: 'IfStatement'
-                        consequent: EMPTY
-                    ]
-                alternate: EMPTY
-            )).to.be.false
-
-            expect(esutils.ast.isProblematicIfStatement(
-                type: 'IfStatement'
-                consequent:
-                    type: 'DoWhileStatement'
-                    body:
-                        type: 'IfStatement'
-                        consequent: EMPTY
-                alternate: EMPTY
-            )).to.be.false
diff --git a/test/ast.js b/test/ast.js
new file mode 100644
index 0000000..aff510b
--- /dev/null
+++ b/test/ast.js
@@ -0,0 +1,311 @@
+/*
+Copyright (C) 2013 Yusuke Suzuki <utatane.tea@gmail.com>
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+  * Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+  * Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in the
+    documentation and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
+DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+import * as esutils from '../src/utils.js';
+
+const EMPTY = {
+    type: 'EmptyStatement'
+};
+
+describe('ast', function() {
+    describe('isExpression', function() {
+        it('returns false if input is not node', function() {
+            expect(esutils.ast.isExpression(0)).to.be.false;
+            expect(esutils.ast.isExpression(null)).to.be.false;
+            expect(esutils.ast.isExpression(void 0)).to.be.false;
+            expect(esutils.ast.isExpression({})).to.be.false;
+            expect(esutils.ast.isExpression({
+                type: null
+            })).to.be.false;
+            expect(esutils.ast.isExpression({
+                type: void 0
+            })).to.be.false;
+        });
+
+        it('returns true if provided node is expression', function() {
+            expect(esutils.ast.isExpression({
+                type: 'ArrayExpression'
+            })).to.be.true;
+            expect(esutils.ast.isExpression({
+                type: 'ThisExpression'
+            })).to.be.true;
+            expect(esutils.ast.isExpression({
+                type: 'Literal',
+                value: 0
+            })).to.be.true;
+        });
+
+        it('returns false if provided node is not expression', function() {
+            expect(esutils.ast.isExpression({
+                type: 'ExpressionStatement'
+            })).to.be.false;
+
+            expect(esutils.ast.isExpression({
+                type: 'Program'
+            })).to.be.false;
+        });
+    });
+    describe('isIterationStatement', function() {
+        it('returns false if input is not node', function() {
+            expect(esutils.ast.isIterationStatement(0)).to.be.false;
+            expect(esutils.ast.isIterationStatement(null)).to.be.false;
+            expect(esutils.ast.isIterationStatement(void 0)).to.be.false;
+            expect(esutils.ast.isIterationStatement({})).to.be.false;
+            expect(esutils.ast.isIterationStatement({
+                type: null
+            })).to.be.false;
+            expect(esutils.ast.isIterationStatement({
+                type: void 0
+            })).to.be.false;
+        });
+        it('returns true if provided node is iteration statement', function() {
+            expect(esutils.ast.isIterationStatement({
+                type: 'ForInStatement'
+            })).to.be.true;
+            expect(esutils.ast.isIterationStatement({
+                type: 'DoWhileStatement'
+            })).to.be.true;
+        });
+        it('returns false if provided node is not iteration statement', function() {
+            expect(esutils.ast.isIterationStatement({
+                type: 'ExpressionStatement'
+            })).to.be.false;
+            expect(esutils.ast.isIterationStatement({
+                type: 'ThisExpression'
+            })).to.be.false;
+        });
+    });
+    describe('isStatement', function() {
+        it('returns false if input is not node', function() {
+            expect(esutils.ast.isStatement(0)).to.be.false;
+            expect(esutils.ast.isStatement(null)).to.be.false;
+            expect(esutils.ast.isStatement(void 0)).to.be.false;
+            expect(esutils.ast.isStatement({})).to.be.false;
+            expect(esutils.ast.isStatement({
+                type: null
+            })).to.be.false;
+            expect(esutils.ast.isStatement({
+                type: void 0
+            })).to.be.false;
+        });
+        it('returns true if provided node is statement', function() {
+            expect(esutils.ast.isStatement({
+                type: 'BlockStatement'
+            })).to.be.true;
+            expect(esutils.ast.isStatement({
+                type: 'ExpressionStatement'
+            })).to.be.true;
+            expect(esutils.ast.isStatement({
+                type: 'WhileStatement'
+            })).to.be.true;
+        });
+        it('returns false if provided node is not statement', function() {
+            expect(esutils.ast.isStatement({
+                type: 'ThisExpression'
+            })).to.be.false;
+            expect(esutils.ast.isStatement({
+                type: 'FunctionDeclaration'
+            })).to.be.false;
+            expect(esutils.ast.isStatement({
+                type: 'Program'
+            })).to.be.false;
+        });
+    });
+    describe('isSourceElement', function() {
+        it('returns false if input is not node', function() {
+            expect(esutils.ast.isSourceElement(0)).to.be.false;
+            expect(esutils.ast.isSourceElement(null)).to.be.false;
+            expect(esutils.ast.isSourceElement(void 0)).to.be.false;
+            expect(esutils.ast.isSourceElement({})).to.be.false;
+            expect(esutils.ast.isSourceElement({
+                type: null
+            })).to.be.false;
+            expect(esutils.ast.isSourceElement({
+                type: void 0
+            })).to.be.false;
+        });
+        it('returns true if provided node is source element', function() {
+            expect(esutils.ast.isSourceElement({
+                type: 'ExpressionStatement'
+            })).to.be.true;
+            expect(esutils.ast.isSourceElement({
+                type: 'WhileStatement'
+            })).to.be.true;
+            expect(esutils.ast.isSourceElement({
+                type: 'FunctionDeclaration'
+            })).to.be.true;
+        });
+        it('returns false if provided node is not source element', function() {
+            expect(esutils.ast.isSourceElement({
+                type: 'ThisExpression'
+            })).to.be.false;
+            expect(esutils.ast.isSourceElement({
+                type: 'Program'
+            })).to.be.false;
+        });
+    });
+    describe('trailingStatement', function() {
+        it('returns trailing statement if node has it', function() {
+            expect(esutils.ast.trailingStatement({
+                type: 'WhileStatement',
+                body: EMPTY
+            })).to.be.eq(EMPTY);
+            expect(esutils.ast.trailingStatement({
+                type: 'WithStatement',
+                body: EMPTY
+            })).to.be.eq(EMPTY);
+            expect(esutils.ast.trailingStatement({
+                type: 'ForStatement',
+                body: EMPTY
+            })).to.be.eq(EMPTY);
+            expect(esutils.ast.trailingStatement({
+                type: 'ForInStatement',
+                body: EMPTY
+            })).to.be.eq(EMPTY);
+            expect(esutils.ast.trailingStatement({
+                type: 'IfStatement',
+                consequent: EMPTY
+            })).to.be.eq(EMPTY);
+            expect(esutils.ast.trailingStatement({
+                type: 'IfStatement',
+                consequent: {
+                    type: 'EmptyStatement'
+                },
+                alternate: EMPTY
+            })).to.be.eq(EMPTY);
+            expect(esutils.ast.trailingStatement({
+                type: 'LabeledStatement',
+                body: EMPTY
+            })).to.be.eq(EMPTY);
+        });
+        it('returns null if node doens\'t have trailing statement', function() {
+            expect(esutils.ast.trailingStatement({
+                type: 'DoWhileStatement',
+                body: EMPTY
+            })).to.be.null;
+            expect(esutils.ast.trailingStatement({
+                type: 'ReturnStatement'
+            })).to.be.null;
+        });
+    });
+    describe('isProblematicIfStatement', function() {
+        it('returns true if node is problematic if statement', function() {
+            expect(esutils.ast.isProblematicIfStatement({
+                type: 'IfStatement',
+                consequent: {
+                    type: 'IfStatement',
+                    consequent: EMPTY
+                },
+                alternate: EMPTY
+            })).to.be.true;
+            expect(esutils.ast.isProblematicIfStatement({
+                type: 'IfStatement',
+                consequent: {
+                    type: 'LabeledStatement',
+                    body: {
+                        type: 'IfStatement',
+                        consequent: EMPTY
+                    }
+                },
+                alternate: EMPTY
+            })).to.be.true;
+            expect(esutils.ast.isProblematicIfStatement({
+                type: 'IfStatement',
+                consequent: {
+                    type: 'WithStatement',
+                    body: {
+                        type: 'IfStatement',
+                        consequent: EMPTY
+                    }
+                },
+                alternate: EMPTY
+            })).to.be.true;
+        });
+        it('returns false if node is not problematic if statement', function() {
+            expect(esutils.ast.isProblematicIfStatement({
+                type: 'ThisExpression'
+            })).to.be.false;
+            expect(esutils.ast.isProblematicIfStatement({
+                type: 'IfStatement',
+                consequent: EMPTY,
+                alternate: EMPTY
+            })).to.be.false;
+            expect(esutils.ast.isProblematicIfStatement({
+                type: 'IfStatement',
+                consequent: {
+                    type: 'IfStatement',
+                    consequent: {
+                        type: 'BlockStatement',
+                        body: []
+                    },
+                    alternate: {
+                        type: 'BlockStatement',
+                        body: []
+                    }
+                },
+                alternate: {
+                    type: 'BlockStatement',
+                    body: []
+                }
+            })).to.be.false;
+            expect(esutils.ast.isProblematicIfStatement({
+                type: 'IfStatement',
+                consequent: {
+                    type: 'BlockStatement',
+                    body: [
+                        {
+                            type: 'IfStatement',
+                            consequent: EMPTY
+                        }
+                    ]
+                },
+                alternate: null
+            })).to.be.false;
+            expect(esutils.ast.isProblematicIfStatement({
+                type: 'IfStatement',
+                consequent: {
+                    type: 'BlockStatement',
+                    body: [
+                        {
+                            type: 'IfStatement',
+                            consequent: EMPTY
+                        }
+                    ]
+                },
+                alternate: EMPTY
+            })).to.be.false;
+            expect(esutils.ast.isProblematicIfStatement({
+                type: 'IfStatement',
+                consequent: {
+                    type: 'DoWhileStatement',
+                    body: {
+                        type: 'IfStatement',
+                        consequent: EMPTY
+                    }
+                },
+                alternate: EMPTY
+            })).to.be.false;
+        });
+    });
+});
diff --git a/test/code.coffee b/test/code.coffee
deleted file mode 100644
index d0eed6f..0000000
--- a/test/code.coffee
+++ /dev/null
@@ -1,184 +0,0 @@
-# Copyright (C) 2013 Yusuke Suzuki <utatane.tea@gmail.com>
-#
-# Redistribution and use in source and binary forms, with or without
-# modification, are permitted provided that the following conditions are met:
-#
-#   * Redistributions of source code must retain the above copyright
-#     notice, this list of conditions and the following disclaimer.
-#   * Redistributions in binary form must reproduce the above copyright
-#     notice, this list of conditions and the following disclaimer in the
-#     documentation and/or other materials provided with the distribution.
-#
-# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
-# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
-# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
-# ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
-# DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
-# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
-# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
-# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
-# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-'use strict'
-
-expect = require('chai').expect
-esutils = require '../'
-
-describe 'code', ->
-    describe 'isDecimalDigit', ->
-        it 'returns true if provided code is decimal digit', ->
-            for ch in [0..9]
-                expect(esutils.code.isDecimalDigit((ch + '').charCodeAt(0))).to.be.true
-
-        it 'returns false if provided code is not decimal digit', ->
-            for code in ['a'.charCodeAt(0)..'z'.charCodeAt(0)]
-                expect(esutils.code.isDecimalDigit(code)).to.be.false
-
-            for code in ['A'.charCodeAt(0)..'Z'.charCodeAt(0)]
-                expect(esutils.code.isDecimalDigit(code)).to.be.false
-
-    describe 'isHexDigit', ->
-        it 'returns true if provided code is hexadecimal digit', ->
-            for ch in [0..9]
-                expect(esutils.code.isHexDigit((ch + '').charCodeAt(0))).to.be.true
-
-            for code in ['a'.charCodeAt(0)..'f'.charCodeAt(0)]
-                expect(esutils.code.isHexDigit(code)).to.be.true
-
-            for code in ['A'.charCodeAt(0)..'F'.charCodeAt(0)]
-                expect(esutils.code.isHexDigit(code)).to.be.true
-
-        it 'returns false if provided code is not hexadecimal digit', ->
-            for code in ['g'.charCodeAt(0)..'z'.charCodeAt(0)]
-                expect(esutils.code.isHexDigit(code)).to.be.false
-
-            for code in ['G'.charCodeAt(0)..'Z'.charCodeAt(0)]
-                expect(esutils.code.isHexDigit(code)).to.be.false
-
-    describe 'isOctalDigit', ->
-        it 'returns true if provided code is octal digit', ->
-            for ch in [0..7]
-                expect(esutils.code.isOctalDigit((ch + '').charCodeAt(0))).to.be.true
-
-        it 'returns false if provided code is not octal digit', ->
-            for ch in [8..9]
-                expect(esutils.code.isOctalDigit((ch + '').charCodeAt(0))).to.be.false
-
-            for code in ['a'.charCodeAt(0)..'z'.charCodeAt(0)]
-                expect(esutils.code.isOctalDigit(code)).to.be.false
-
-            for code in ['A'.charCodeAt(0)..'Z'.charCodeAt(0)]
-                expect(esutils.code.isOctalDigit(code)).to.be.false
-
-    describe 'isWhiteSpace', ->
-        it 'returns true if provided code is white space', ->
-            codes = [
-                0x0009  # TAB
-                0x000B  # VT
-                0x000C  # FF
-                0x0020  # SP
-                0x00A0  # NBSP
-                0xFEFF  # BOM
-
-                # Zs
-                0x1680
-                0x2000
-                0x2001
-                0x2002
-                0x2003
-                0x2004
-                0x2005
-                0x2006
-                0x2007
-                0x2008
-                0x2009
-                0x200A
-                0x202F
-                0x205F
-                0x3000
-            ]
-            for code in codes
-                expect(esutils.code.isWhiteSpace(code)).to.be.true
-
-            expect(esutils.code.isWhiteSpace(0x180E)).to.be.false
-
-        it 'returns false if provided code is not white space', ->
-            for ch in [0..9]
-                expect(esutils.code.isWhiteSpace((ch + '').charCodeAt(0))).to.be.false
-
-            for code in ['a'.charCodeAt(0)..'z'.charCodeAt(0)]
-                expect(esutils.code.isWhiteSpace(code)).to.be.false
-
-            for code in ['A'.charCodeAt(0)..'Z'.charCodeAt(0)]
-                expect(esutils.code.isWhiteSpace(code)).to.be.false
-
-    describe 'isLineTerminator', ->
-        it 'returns true if provided code is line terminator', ->
-            codes = [
-                0x000A
-                0x000D
-                0x2028
-                0x2029
-            ]
-            for code in codes
-                expect(esutils.code.isLineTerminator(code)).to.be.true
-
-        it 'returns false if provided code is not line terminator', ->
-            for ch in [0..9]
-                expect(esutils.code.isLineTerminator((ch + '').charCodeAt(0))).to.be.false
-
-            for code in ['a'.charCodeAt(0)..'z'.charCodeAt(0)]
-                expect(esutils.code.isLineTerminator(code)).to.be.false
-
-            for code in ['A'.charCodeAt(0)..'Z'.charCodeAt(0)]
-                expect(esutils.code.isLineTerminator(code)).to.be.false
-
-    describe 'isIdentifierStartES5', ->
-        it 'returns true if provided code can be a start of Identifier in ES5', ->
-            characters = ['a', '_', '$', 'ゆ']
-            for code in characters.map((ch) -> ch.charCodeAt(0))
-                expect(esutils.code.isIdentifierStartES5(code)).to.be.true
-
-        it 'returns false if provided code cannot be a start of Identifier in ES5', ->
-            for ch in [0..9]
-                expect(esutils.code.isIdentifierStartES5((ch + '').charCodeAt(0))).to.be.false
-
-    describe 'isIdentifierPartES5', ->
-        it 'returns true if provided code can be a part of Identifier in ES5', ->
-            characters = ['a', '_', '$', 'ゆ']
-            for code in characters.map((ch) -> ch.charCodeAt(0))
-                expect(esutils.code.isIdentifierPartES5(code)).to.be.true
-
-            for ch in [0..9]
-                expect(esutils.code.isIdentifierPartES5((ch + '').charCodeAt(0))).to.be.true
-
-        it 'returns false if provided code cannot be a part of Identifier in ES5', ->
-            expect(esutils.code.isIdentifierPartES5('+'.charCodeAt(0))).to.be.false
-            expect(esutils.code.isIdentifierPartES5('-'.charCodeAt(0))).to.be.false
-
-    describe 'isIdentifierStartES6', ->
-        it 'returns true if provided code can be a start of Identifier in ES6', ->
-            characters = ['a', '_', '$', 'ゆ', '\u0AF9']
-            for code in characters.map((ch) -> ch.charCodeAt(0))
-                expect(esutils.code.isIdentifierStartES6(code)).to.be.true
-
-        it 'returns false if provided code cannot be a start of Identifier in ES6', ->
-            for ch in [0..9]
-                expect(esutils.code.isIdentifierStartES6((ch + '').charCodeAt(0))).to.be.false
-
-    describe 'isIdentifierPartES6', ->
-        it 'returns true if provided code can be a part of Identifier in ES6', ->
-            characters = ['a', '_', '$', 'ゆ']
-            for code in characters.map((ch) -> ch.charCodeAt(0))
-                expect(esutils.code.isIdentifierPartES6(code)).to.be.true
-
-            for ch in [0..9]
-                expect(esutils.code.isIdentifierPartES6((ch + '').charCodeAt(0))).to.be.true
-
-        it 'supports astral symbols', ->
-            expect(esutils.code.isIdentifierPartES6(0xE01D5)).to.be.true
-
-        it 'returns false if provided code cannot be a part of Identifier in ES6', ->
-            expect(esutils.code.isIdentifierPartES6('+'.charCodeAt(0))).to.be.false
-            expect(esutils.code.isIdentifierPartES6('-'.charCodeAt(0))).to.be.false
diff --git a/test/code.js b/test/code.js
new file mode 100644
index 0000000..c462b0e
--- /dev/null
+++ b/test/code.js
@@ -0,0 +1,266 @@
+/*
+Copyright (C) 2013 Yusuke Suzuki <utatane.tea@gmail.com>
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+  * Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+  * Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in the
+    documentation and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
+DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+import * as esutils from '../src/utils.js';
+
+describe('code', function() {
+    describe('isDecimalDigit', function() {
+        it('returns true if provided code is decimal digit', function() {
+            const results = [];
+            for (let ch = 0, i = 0; i <= 9; ch = ++i) {
+                results.push(expect(esutils.code.isDecimalDigit((String(ch)).charCodeAt(0))).to.be.true);
+            }
+            return results;
+        });
+
+        it('returns false if provided code is not decimal digit', function() {
+            let code, i, ref, ref1;
+            for (code = i = ref = 'a'.charCodeAt(0), ref1 = 'z'.charCodeAt(0); (ref <= ref1 ? i <= ref1 : i >= ref1); code = ref <= ref1 ? ++i : --i) {
+                expect(esutils.code.isDecimalDigit(code)).to.be.false;
+            }
+            const results = [];
+
+            let j, ref2, ref3;
+            for (code = j = ref2 = 'A'.charCodeAt(0), ref3 = 'Z'.charCodeAt(0); (ref2 <= ref3 ? j <= ref3 : j >= ref3); code = ref2 <= ref3 ? ++j : --j) {
+                results.push(expect(esutils.code.isDecimalDigit(code)).to.be.false);
+            }
+            return results;
+        });
+    });
+    describe('isHexDigit', function() {
+        it('returns true if provided code is hexadecimal digit', function() {
+            for (let ch = 0, i = 0; i <= 9; ch = ++i) {
+                expect(esutils.code.isHexDigit((String(ch)).charCodeAt(0))).to.be.true;
+            }
+            let j, ref, ref1, code;
+            for (code = j = ref = 'a'.charCodeAt(0), ref1 = 'f'.charCodeAt(0); (ref <= ref1 ? j <= ref1 : j >= ref1); code = ref <= ref1 ? ++j : --j) {
+                expect(esutils.code.isHexDigit(code)).to.be.true;
+            }
+            const results = [];
+            let k, ref2, ref3;
+            for (code = k = ref2 = 'A'.charCodeAt(0), ref3 = 'F'.charCodeAt(0); (ref2 <= ref3 ? k <= ref3 : k >= ref3); code = ref2 <= ref3 ? ++k : --k) {
+                results.push(expect(esutils.code.isHexDigit(code)).to.be.true);
+            }
+            return results;
+        });
+
+        it('returns false if provided code is not hexadecimal digit', function() {
+            let code, i, ref, ref1;
+            for (code = i = ref = 'g'.charCodeAt(0), ref1 = 'z'.charCodeAt(0); (ref <= ref1 ? i <= ref1 : i >= ref1); code = ref <= ref1 ? ++i : --i) {
+                expect(esutils.code.isHexDigit(code)).to.be.false;
+            }
+            const results = [];
+            let j, ref2, ref3;
+            for (code = j = ref2 = 'G'.charCodeAt(0), ref3 = 'Z'.charCodeAt(0); (ref2 <= ref3 ? j <= ref3 : j >= ref3); code = ref2 <= ref3 ? ++j : --j) {
+                results.push(expect(esutils.code.isHexDigit(code)).to.be.false);
+            }
+            return results;
+        });
+    });
+    describe('isOctalDigit', function() {
+        it('returns true if provided code is octal digit', function() {
+            const results = [];
+            for (let ch = 0, i = 0; i <= 7; ch = ++i) {
+                results.push(expect(esutils.code.isOctalDigit((String(ch)).charCodeAt(0))).to.be.true);
+            }
+            return results;
+        });
+
+        it('returns false if provided code is not octal digit', function() {
+            for (let ch = 8, i = 8; i <= 9; ch = ++i) {
+                expect(esutils.code.isOctalDigit((String(ch)).charCodeAt(0))).to.be.false;
+            }
+            let code, j, ref, ref1;
+            for (code = j = ref = 'a'.charCodeAt(0), ref1 = 'z'.charCodeAt(0); (ref <= ref1 ? j <= ref1 : j >= ref1); code = ref <= ref1 ? ++j : --j) {
+                expect(esutils.code.isOctalDigit(code)).to.be.false;
+            }
+            const results = [];
+            let k, ref2, ref3;
+            for (code = k = ref2 = 'A'.charCodeAt(0), ref3 = 'Z'.charCodeAt(0); (ref2 <= ref3 ? k <= ref3 : k >= ref3); code = ref2 <= ref3 ? ++k : --k) {
+                results.push(expect(esutils.code.isOctalDigit(code)).to.be.false);
+            }
+            return results;
+        });
+    });
+    describe('isWhiteSpace', function() {
+        it('returns true if provided code is white space', function() {
+            const codes = [
+                0x0009, // TAB
+                0x000B, // VT
+                0x000C, // FF
+                0x0020, // SP
+                0x00A0, // NBSP
+                0xFEFF, // BOM
+
+                // Zs
+                0x1680,
+                0x2000,
+                0x2001,
+                0x2002,
+                0x2003,
+                0x2004,
+                0x2005,
+                0x2006,
+                0x2007,
+                0x2008,
+                0x2009,
+                0x200A,
+                0x202F,
+                0x205F,
+                0x3000
+            ];
+            for (const code of codes) {
+                expect(esutils.code.isWhiteSpace(code)).to.be.true;
+            }
+            expect(esutils.code.isWhiteSpace(0x180E)).to.be.false;
+        });
+
+        it('returns false if provided code is not white space', function() {
+            for (let ch = 0, i = 0; i <= 9; ch = ++i) {
+                expect(esutils.code.isWhiteSpace((String(ch)).charCodeAt(0))).to.be.false;
+            }
+            let code, j, ref, ref1;
+            for (code = j = ref = 'a'.charCodeAt(0), ref1 = 'z'.charCodeAt(0); (ref <= ref1 ? j <= ref1 : j >= ref1); code = ref <= ref1 ? ++j : --j) {
+                expect(esutils.code.isWhiteSpace(code)).to.be.false;
+            }
+            const results = [];
+            let k, ref2, ref3;
+            for (code = k = ref2 = 'A'.charCodeAt(0), ref3 = 'Z'.charCodeAt(0); (ref2 <= ref3 ? k <= ref3 : k >= ref3); code = ref2 <= ref3 ? ++k : --k) {
+                results.push(expect(esutils.code.isWhiteSpace(code)).to.be.false);
+            }
+            return results;
+        });
+    });
+    describe('isLineTerminator', function() {
+        it('returns true if provided code is line terminator', function() {
+            const codes = [0x000A, 0x000D, 0x2028, 0x2029];
+            const results = [];
+            for (const code of codes) {
+                results.push(expect(esutils.code.isLineTerminator(code)).to.be.true);
+            }
+            return results;
+        });
+
+        it('returns false if provided code is not line terminator', function() {
+            for (let ch = 0, i = 0; i <= 9; ch = ++i) {
+                expect(esutils.code.isLineTerminator((String(ch)).charCodeAt(0))).to.be.false;
+            }
+            let code, j, ref, ref1;
+            for (code = j = ref = 'a'.charCodeAt(0), ref1 = 'z'.charCodeAt(0); (ref <= ref1 ? j <= ref1 : j >= ref1); code = ref <= ref1 ? ++j : --j) {
+                expect(esutils.code.isLineTerminator(code)).to.be.false;
+            }
+            const results = [];
+            let k, ref2, ref3;
+            for (code = k = ref2 = 'A'.charCodeAt(0), ref3 = 'Z'.charCodeAt(0); (ref2 <= ref3 ? k <= ref3 : k >= ref3); code = ref2 <= ref3 ? ++k : --k) {
+                results.push(expect(esutils.code.isLineTerminator(code)).to.be.false);
+            }
+            return results;
+        });
+    });
+    describe('isIdentifierStartES5', function() {
+        it('returns true if provided code can be a start of Identifier in ES5', function() {
+            const characters = ['a', '_', '$', 'ゆ'];
+            const ref = characters.map(function(ch) {
+                return ch.charCodeAt(0);
+            });
+            const results = [];
+            for (const code of ref) {
+                results.push(expect(esutils.code.isIdentifierStartES5(code)).to.be.true);
+            }
+            return results;
+        });
+        it('returns false if provided code cannot be a start of Identifier in ES5', function() {
+            const results = [];
+            for (let ch = 0, i = 0; i <= 9; ch = ++i) {
+                results.push(expect(esutils.code.isIdentifierStartES5((String(ch)).charCodeAt(0))).to.be.false);
+            }
+            return results;
+        });
+    });
+    describe('isIdentifierPartES5', function() {
+        it('returns true if provided code can be a part of Identifier in ES5', function() {
+            const characters = ['a', '_', '$', 'ゆ'];
+            const ref = characters.map(function(ch) {
+                return ch.charCodeAt(0);
+            });
+            for (const code of ref) {
+                expect(esutils.code.isIdentifierPartES5(code)).to.be.true;
+            }
+            const results = [];
+            for (let ch = 0, j = 0; j <= 9; ch = ++j) {
+                results.push(expect(esutils.code.isIdentifierPartES5((String(ch)).charCodeAt(0))).to.be.true);
+            }
+            return results;
+        });
+        it('returns false if provided code cannot be a part of Identifier in ES5', function() {
+            expect(esutils.code.isIdentifierPartES5('+'.charCodeAt(0))).to.be.false;
+            expect(esutils.code.isIdentifierPartES5('-'.charCodeAt(0))).to.be.false;
+        });
+    });
+    describe('isIdentifierStartES6', function() {
+        it('returns true if provided code can be a start of Identifier in ES6', function() {
+            const characters = ['a', '_', '$', 'ゆ', '\u0AF9'];
+            const ref = characters.map(function(ch) {
+                return ch.charCodeAt(0);
+            });
+            const results = [];
+            for (const code of ref) {
+                results.push(expect(esutils.code.isIdentifierStartES6(code)).to.be.true);
+            }
+            return results;
+        });
+
+        it('returns false if provided code cannot be a start of Identifier in ES6', function() {
+            const results = [];
+            for (let ch = 0, i = 0; i <= 9; ch = ++i) {
+                results.push(expect(esutils.code.isIdentifierStartES6((String(ch)).charCodeAt(0))).to.be.false);
+            }
+            return results;
+        });
+    });
+
+    describe('isIdentifierPartES6', function() {
+        it('returns true if provided code can be a part of Identifier in ES6', function() {
+            const characters = ['a', '_', '$', 'ゆ'];
+            const ref = characters.map(function(ch) {
+                return ch.charCodeAt(0);
+            });
+            for (const code of ref) {
+                expect(esutils.code.isIdentifierPartES6(code)).to.be.true;
+            }
+            const results = [];
+            for (let ch = 0, j = 0; j <= 9; ch = ++j) {
+                results.push(expect(esutils.code.isIdentifierPartES6((String(ch)).charCodeAt(0))).to.be.true);
+            }
+            return results;
+        });
+        it('supports astral symbols', function() {
+            expect(esutils.code.isIdentifierPartES6(0xE01D5)).to.be.true;
+        });
+        it('returns false if provided code cannot be a part of Identifier in ES6', function() {
+            expect(esutils.code.isIdentifierPartES6('+'.charCodeAt(0))).to.be.false;
+            expect(esutils.code.isIdentifierPartES6('-'.charCodeAt(0))).to.be.false;
+        });
+    });
+});
diff --git a/test/keyword.coffee b/test/keyword.coffee
deleted file mode 100644
index 9fef055..0000000
--- a/test/keyword.coffee
+++ /dev/null
@@ -1,400 +0,0 @@
-# Copyright (C) 2013 Yusuke Suzuki <utatane.tea@gmail.com>
-#
-# Redistribution and use in source and binary forms, with or without
-# modification, are permitted provided that the following conditions are met:
-#
-#   * Redistributions of source code must retain the above copyright
-#     notice, this list of conditions and the following disclaimer.
-#   * Redistributions in binary form must reproduce the above copyright
-#     notice, this list of conditions and the following disclaimer in the
-#     documentation and/or other materials provided with the distribution.
-#
-# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
-# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
-# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
-# ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
-# DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
-# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
-# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
-# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
-# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-'use strict'
-
-expect = require('chai').expect
-esutils = require '../'
-
-KW = [
-    'if'
-    'in'
-    'do'
-    'var'
-    'for'
-    'new'
-    'try'
-    'this'
-    'else'
-    'case'
-    'void'
-    'with'
-    'enum'
-    'while'
-    'break'
-    'catch'
-    'throw'
-    'const'
-    'class'
-    'super'
-    'return'
-    'typeof'
-    'delete'
-    'switch'
-    'export'
-    'import'
-    'default'
-    'finally'
-    'extends'
-    'function'
-    'continue'
-    'debugger'
-    'instanceof'
-]
-
-SRW = [
-    'implements'
-    'interface'
-    'package'
-    'private'
-    'protected'
-    'public'
-    'static'
-    'let'
-]
-
-describe 'keyword', ->
-    describe 'isKeywordES6', ->
-        it 'returns true if provided string is keyword under non-strict mode', ->
-            for word in KW
-                expect(esutils.keyword.isKeywordES6(word, no)).to.be.true
-
-            expect(esutils.keyword.isKeywordES6('yield', no)).to.be.true
-
-        it 'returns false if provided string is not keyword under non-strict mode', ->
-            words = [
-                'hello'
-                '20'
-                '$'
-                'ゆゆ式'
-            ]
-
-            for word in words
-                expect(esutils.keyword.isKeywordES6(word, no)).to.be.false
-
-            for word in SRW
-                expect(esutils.keyword.isKeywordES6(word, no)).to.be.false
-
-        it 'returns true if provided string is keyword under strict mode', ->
-            for word in KW
-                expect(esutils.keyword.isKeywordES6(word, yes)).to.be.true
-
-            expect(esutils.keyword.isKeywordES6('yield', yes)).to.be.true
-
-            for word in SRW
-                expect(esutils.keyword.isKeywordES6(word, yes)).to.be.true
-
-
-        it 'returns false if provided string is not keyword under strict mode', ->
-            words = [
-                'hello'
-                '20'
-                '$'
-                'ゆゆ式'
-            ]
-
-            for word in words
-                expect(esutils.keyword.isKeywordES6(word, yes)).to.be.false
-
-
-    describe 'isKeywordES5', ->
-        it 'returns true if provided string is keyword under non-strict mode', ->
-            for word in KW
-                expect(esutils.keyword.isKeywordES5(word, no)).to.be.true
-
-        it 'returns false if provided string is not keyword under non-strict mode', ->
-            words = [
-                'hello'
-                '20'
-                '$'
-                'ゆゆ式'
-            ]
-
-            for word in words
-                expect(esutils.keyword.isKeywordES5(word, no)).to.be.false
-
-            for word in SRW
-                expect(esutils.keyword.isKeywordES5(word, no)).to.be.false
-
-            expect(esutils.keyword.isKeywordES5('yield', no)).to.be.false
-
-        it 'returns true if provided string is keyword under strict mode', ->
-            for word in KW
-                expect(esutils.keyword.isKeywordES5(word, yes)).to.be.true
-
-            expect(esutils.keyword.isKeywordES5('yield', yes)).to.be.true
-
-            for word in SRW
-                expect(esutils.keyword.isKeywordES5(word, yes)).to.be.true
-
-
-        it 'returns false if provided string is not keyword under strict mode', ->
-            words = [
-                'hello'
-                '20'
-                '$'
-                'ゆゆ式'
-            ]
-
-            for word in words
-                expect(esutils.keyword.isKeywordES5(word, yes)).to.be.false
-
-
-    describe 'isReservedWordES6', ->
-        it 'returns true for null/boolean values', ->
-            expect(esutils.keyword.isReservedWordES6('null', no)).to.be.true
-            expect(esutils.keyword.isReservedWordES6('null', yes)).to.be.true
-            expect(esutils.keyword.isReservedWordES6('true', no)).to.be.true
-            expect(esutils.keyword.isReservedWordES6('true', yes)).to.be.true
-            expect(esutils.keyword.isReservedWordES6('false', no)).to.be.true
-            expect(esutils.keyword.isReservedWordES6('false', yes)).to.be.true
-
-        # isReservedWordES6 has the same properties as isKeywordES6
-
-        it 'returns true if provided string is keyword under non-strict mode', ->
-            for word in KW
-                expect(esutils.keyword.isReservedWordES6(word, no)).to.be.true
-
-            expect(esutils.keyword.isReservedWordES6('yield', no)).to.be.true
-
-        it 'returns false if provided string is not keyword under non-strict mode', ->
-            words = [
-                'hello'
-                '20'
-                '$'
-                'ゆゆ式'
-            ]
-
-            for word in words
-                expect(esutils.keyword.isReservedWordES6(word, no)).to.be.false
-
-            for word in SRW
-                expect(esutils.keyword.isReservedWordES6(word, no)).to.be.false
-
-        it 'returns true if provided string is keyword under strict mode', ->
-            for word in KW
-                expect(esutils.keyword.isReservedWordES6(word, yes)).to.be.true
-
-            expect(esutils.keyword.isReservedWordES6('yield', yes)).to.be.true
-
-            for word in SRW
-                expect(esutils.keyword.isReservedWordES6(word, yes)).to.be.true
-
-
-        it 'returns false if provided string is not keyword under strict mode', ->
-            words = [
-                'hello'
-                '20'
-                '$'
-                'ゆゆ式'
-            ]
-
-            for word in words
-                expect(esutils.keyword.isReservedWordES6(word, yes)).to.be.false
-
-
-    describe 'isReservedWordES5', ->
-        it 'returns true for null/boolean values', ->
-            expect(esutils.keyword.isReservedWordES5('null', no)).to.be.true
-            expect(esutils.keyword.isReservedWordES5('null', yes)).to.be.true
-            expect(esutils.keyword.isReservedWordES5('true', no)).to.be.true
-            expect(esutils.keyword.isReservedWordES5('true', yes)).to.be.true
-            expect(esutils.keyword.isReservedWordES5('false', no)).to.be.true
-            expect(esutils.keyword.isReservedWordES5('false', yes)).to.be.true
-
-        # isReservedWordES5 has the same properties as isKeywordES5
-
-        it 'returns true if provided string is keyword under non-strict mode', ->
-            for word in KW
-                expect(esutils.keyword.isReservedWordES5(word, no)).to.be.true
-
-        it 'returns false if provided string is not keyword under non-strict mode', ->
-            words = [
-                'hello'
-                '20'
-                '$'
-                'ゆゆ式'
-            ]
-
-            for word in words
-                expect(esutils.keyword.isReservedWordES5(word, no)).to.be.false
-
-            for word in SRW
-                expect(esutils.keyword.isReservedWordES5(word, no)).to.be.false
-
-            expect(esutils.keyword.isReservedWordES5('yield', no)).to.be.false
-
-        it 'returns true if provided string is keyword under strict mode', ->
-            for word in KW
-                expect(esutils.keyword.isReservedWordES5(word, yes)).to.be.true
-
-            expect(esutils.keyword.isReservedWordES5('yield', yes)).to.be.true
-
-            for word in SRW
-                expect(esutils.keyword.isReservedWordES5(word, yes)).to.be.true
-
-
-        it 'returns false if provided string is not keyword under strict mode', ->
-            words = [
-                'hello'
-                '20'
-                '$'
-                'ゆゆ式'
-            ]
-
-            for word in words
-                expect(esutils.keyword.isReservedWordES5(word, yes)).to.be.false
-
-
-    describe 'isRestrictedWord', ->
-        it 'returns true if provided string is "eval" or "arguments"', ->
-            expect(esutils.keyword.isRestrictedWord('eval')).to.be.true
-            expect(esutils.keyword.isRestrictedWord('arguments')).to.be.true
-
-        it 'returns false if provided string is not "eval" or "arguments"', ->
-            words = [
-                'hello'
-                '20'
-                '$'
-                'ゆゆ式'
-            ]
-
-            for word in words
-                expect(esutils.keyword.isRestrictedWord(word)).to.be.false
-
-
-    describe 'isIdentifierName', ->
-        it 'returns false if provided string is empty', ->
-            expect(esutils.keyword.isIdentifierNameES5('')).to.be.false
-            expect(esutils.keyword.isIdentifierNameES6('')).to.be.false
-
-        it 'returns true if provided string is IdentifierName', ->
-            words = [
-                'hello'
-                '$'
-                'ゆゆ式'
-                '$20'
-                'hello20'
-                '_'
-                'if'
-            ]
-
-            for word in words
-                expect(esutils.keyword.isIdentifierNameES5(word)).to.be.true
-                expect(esutils.keyword.isIdentifierNameES6(word)).to.be.true
-
-
-        it 'returns false if provided string is not IdentifierName', ->
-            words = [
-                '+hello'
-                '0$'
-                '-ゆゆ式'
-                '#_'
-                '_#'
-            ]
-
-            for word in words
-                expect(esutils.keyword.isIdentifierNameES5(word)).to.be.false
-                expect(esutils.keyword.isIdentifierNameES6(word)).to.be.false
-
-        it 'supports astral symbols', ->
-            expect(esutils.keyword.isIdentifierNameES6('x\uDB40\uDDD5')).to.be.true
-
-
-    describe 'isIdentifierES5', ->
-        it 'returns false if provided string is empty', ->
-            expect(esutils.keyword.isIdentifierES5('')).to.be.false
-
-        it 'returns true if provided string is Identifier', ->
-            words = [
-                'hello'
-                '$'
-                'ゆゆ式'
-                '$20'
-                'hello20'
-                '_'
-            ]
-
-            for word in words
-                expect(esutils.keyword.isIdentifierES5(word)).to.be.true
-
-            expect(esutils.keyword.isIdentifierES5('yield', no)).to.be.true
-            expect(esutils.keyword.isIdentifierES5('let', no)).to.be.true
-
-        it 'returns false if provided string is not Identifier', ->
-            words = [
-                '+hello'
-                '0$'
-                '-ゆゆ式'
-                '#_'
-                '_#'
-                'if'
-                'null'
-                'true'
-                'false'
-            ]
-
-            for word in words
-                expect(esutils.keyword.isIdentifierES5(word)).to.be.false
-
-            expect(esutils.keyword.isIdentifierES5('yield', yes)).to.be.false
-            expect(esutils.keyword.isIdentifierES5('let', yes)).to.be.false
-
-
-    describe 'isIdentifierES6', ->
-        it 'returns false if provided string is empty', ->
-            expect(esutils.keyword.isIdentifierES6('')).to.be.false
-
-        it 'returns true if provided string is Identifier', ->
-            words = [
-                'hello'
-                '$'
-                'ゆゆ式'
-                '$20'
-                'hello20'
-                '_'
-            ]
-
-            for word in words
-                expect(esutils.keyword.isIdentifierES6(word)).to.be.true
-
-            expect(esutils.keyword.isIdentifierES6('let', no)).to.be.true
-
-        it 'returns false if provided string is not Identifier', ->
-            words = [
-                '+hello'
-                '0$'
-                '-ゆゆ式'
-                '#_'
-                '_#'
-                'if'
-                'null'
-                'true'
-                'false'
-            ]
-
-            for word in words
-                expect(esutils.keyword.isIdentifierES6(word)).to.be.false
-
-            expect(esutils.keyword.isIdentifierES6('yield', no)).to.be.false
-            expect(esutils.keyword.isIdentifierES6('yield', yes)).to.be.false
-            expect(esutils.keyword.isIdentifierES6('let', yes)).to.be.false
diff --git a/test/keyword.js b/test/keyword.js
new file mode 100644
index 0000000..0d6926a
--- /dev/null
+++ b/test/keyword.js
@@ -0,0 +1,298 @@
+/*
+Copyright (C) 2013 Yusuke Suzuki <utatane.tea@gmail.com>
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+  * Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+  * Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in the
+    documentation and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
+DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+import * as esutils from '../src/utils.js';
+
+const KW = ['if', 'in', 'do', 'var', 'for', 'new', 'try', 'this', 'else', 'case', 'void', 'with', 'enum', 'while', 'break', 'catch', 'throw', 'const', 'class', 'super', 'return', 'typeof', 'delete', 'switch', 'export', 'import', 'default', 'finally', 'extends', 'function', 'continue', 'debugger', 'instanceof'];
+
+const SRW = ['implements', 'interface', 'package', 'private', 'protected', 'public', 'static', 'let'];
+
+describe('keyword', function() {
+    describe('isKeywordES6', function() {
+        it('returns true if provided string is keyword under non-strict mode', function() {
+            for (const word of KW) {
+                expect(esutils.keyword.isKeywordES6(word, false)).to.be.true;
+            }
+            expect(esutils.keyword.isKeywordES6('yield', false)).to.be.true;
+        });
+        it('returns false if provided string is not keyword under non-strict mode', function() {
+            const words = ['hello', '20', '$', 'ゆゆ式'];
+            for (const word of words) {
+                expect(esutils.keyword.isKeywordES6(word, false)).to.be.false;
+            }
+            const results = [];
+            for (const word of SRW) {
+                results.push(expect(esutils.keyword.isKeywordES6(word, false)).to.be.false);
+            }
+            return results;
+        });
+        it('returns true if provided string is keyword under strict mode', function() {
+            for (const word of KW) {
+                expect(esutils.keyword.isKeywordES6(word, true)).to.be.true;
+            }
+            expect(esutils.keyword.isKeywordES6('yield', true)).to.be.true;
+            const results = [];
+            for (const word of SRW) {
+                results.push(expect(esutils.keyword.isKeywordES6(word, true)).to.be.true);
+            }
+            return results;
+        });
+        it('returns false if provided string is not keyword under strict mode', function() {
+            const words = ['hello', '20', '$', 'ゆゆ式'];
+            const results = [];
+            for (const word of words) {
+                results.push(expect(esutils.keyword.isKeywordES6(word, true)).to.be.false);
+            }
+            return results;
+        });
+    });
+    describe('isKeywordES5', function() {
+        it('returns true if provided string is keyword under non-strict mode', function() {
+            const results = [];
+            for (const word of KW) {
+                results.push(expect(esutils.keyword.isKeywordES5(word, false)).to.be.true);
+            }
+            return results;
+        });
+        it('returns false if provided string is not keyword under non-strict mode', function() {
+            const words = ['hello', '20', '$', 'ゆゆ式'];
+            for (const word of words) {
+                expect(esutils.keyword.isKeywordES5(word, false)).to.be.false;
+            }
+            for (const word of SRW) {
+                expect(esutils.keyword.isKeywordES5(word, false)).to.be.false;
+            }
+            expect(esutils.keyword.isKeywordES5('yield', false)).to.be.false;
+        });
+        it('returns true if provided string is keyword under strict mode', function() {
+            for (const word of KW) {
+                expect(esutils.keyword.isKeywordES5(word, true)).to.be.true;
+            }
+            expect(esutils.keyword.isKeywordES5('yield', true)).to.be.true;
+            const results = [];
+            for (const word of SRW) {
+                results.push(expect(esutils.keyword.isKeywordES5(word, true)).to.be.true);
+            }
+            return results;
+        });
+
+        it('returns false if provided string is not keyword under strict mode', function() {
+            const words = ['hello', '20', '$', 'ゆゆ式'];
+            const results = [];
+            for (const word of words) {
+                results.push(expect(esutils.keyword.isKeywordES5(word, true)).to.be.false);
+            }
+            return results;
+        });
+    });
+    describe('isReservedWordES6', function() {
+        it('returns true for null/boolean values', function() {
+            expect(esutils.keyword.isReservedWordES6('null', false)).to.be.true;
+            expect(esutils.keyword.isReservedWordES6('null', true)).to.be.true;
+            expect(esutils.keyword.isReservedWordES6('true', false)).to.be.true;
+            expect(esutils.keyword.isReservedWordES6('true', true)).to.be.true;
+            expect(esutils.keyword.isReservedWordES6('false', false)).to.be.true;
+            expect(esutils.keyword.isReservedWordES6('false', true)).to.be.true;
+        });
+        // isReservedWordES6 has the same properties as isKeywordES6
+        it('returns true if provided string is keyword under non-strict mode', function() {
+            for (const word of KW) {
+                expect(esutils.keyword.isReservedWordES6(word, false)).to.be.true;
+            }
+            expect(esutils.keyword.isReservedWordES6('yield', false)).to.be.true;
+        });
+        it('returns false if provided string is not keyword under non-strict mode', function() {
+            const words = ['hello', '20', '$', 'ゆゆ式'];
+            for (const word of words) {
+                expect(esutils.keyword.isReservedWordES6(word, false)).to.be.false;
+            }
+            const results = [];
+            for (const word of SRW) {
+                results.push(expect(esutils.keyword.isReservedWordES6(word, false)).to.be.false);
+            }
+            return results;
+        });
+        it('returns true if provided string is keyword under strict mode', function() {
+            for (const word of KW) {
+                expect(esutils.keyword.isReservedWordES6(word, true)).to.be.true;
+            }
+            expect(esutils.keyword.isReservedWordES6('yield', true)).to.be.true;
+            const results = [];
+            for (const word of SRW) {
+                results.push(expect(esutils.keyword.isReservedWordES6(word, true)).to.be.true);
+            }
+            return results;
+        });
+        it('returns false if provided string is not keyword under strict mode', function() {
+            const words = ['hello', '20', '$', 'ゆゆ式'];
+            const results = [];
+            for (const word of words) {
+                results.push(expect(esutils.keyword.isReservedWordES6(word, true)).to.be.false);
+            }
+            return results;
+        });
+    });
+    describe('isReservedWordES5', function() {
+        it('returns true for null/boolean values', function() {
+            expect(esutils.keyword.isReservedWordES5('null', false)).to.be.true;
+            expect(esutils.keyword.isReservedWordES5('null', true)).to.be.true;
+            expect(esutils.keyword.isReservedWordES5('true', false)).to.be.true;
+            expect(esutils.keyword.isReservedWordES5('true', true)).to.be.true;
+            expect(esutils.keyword.isReservedWordES5('false', false)).to.be.true;
+            expect(esutils.keyword.isReservedWordES5('false', true)).to.be.true;
+        });
+        // isReservedWordES5 has the same properties as isKeywordES5
+        it('returns true if provided string is keyword under non-strict mode', function() {
+            const results = [];
+            for (const word of KW) {
+                results.push(expect(esutils.keyword.isReservedWordES5(word, false)).to.be.true);
+            }
+            return results;
+        });
+        it('returns false if provided string is not keyword under non-strict mode', function() {
+            const words = ['hello', '20', '$', 'ゆゆ式'];
+            for (const word of words) {
+                expect(esutils.keyword.isReservedWordES5(word, false)).to.be.false;
+            }
+            for (const word of SRW) {
+                expect(esutils.keyword.isReservedWordES5(word, false)).to.be.false;
+            }
+            expect(esutils.keyword.isReservedWordES5('yield', false)).to.be.false;
+        });
+
+        it('returns true if provided string is keyword under strict mode', function() {
+            for (const word of KW) {
+                expect(esutils.keyword.isReservedWordES5(word, true)).to.be.true;
+            }
+            expect(esutils.keyword.isReservedWordES5('yield', true)).to.be.true;
+            const results = [];
+            for (const word of SRW) {
+                results.push(expect(esutils.keyword.isReservedWordES5(word, true)).to.be.true);
+            }
+            return results;
+        });
+
+        it('returns false if provided string is not keyword under strict mode', function() {
+            const words = ['hello', '20', '$', 'ゆゆ式'];
+            const results = [];
+            for (const word of words) {
+                results.push(expect(esutils.keyword.isReservedWordES5(word, true)).to.be.false);
+            }
+            return results;
+        });
+    });
+    describe('isRestrictedWord', function() {
+        it('returns true if provided string is "eval" or "arguments"', function() {
+            expect(esutils.keyword.isRestrictedWord('eval')).to.be.true;
+            expect(esutils.keyword.isRestrictedWord('arguments')).to.be.true;
+        });
+
+        it('returns false if provided string is not "eval" or "arguments"', function() {
+            const words = ['hello', '20', '$', 'ゆゆ式'];
+            const results = [];
+            for (const word of words) {
+                results.push(expect(esutils.keyword.isRestrictedWord(word)).to.be.false);
+            }
+            return results;
+        });
+    });
+    describe('isIdentifierName', function() {
+        it('returns false if provided string is empty', function() {
+            expect(esutils.keyword.isIdentifierNameES5('')).to.be.false;
+            expect(esutils.keyword.isIdentifierNameES6('')).to.be.false;
+        });
+        it('returns true if provided string is IdentifierName', function() {
+            const words = ['hello', '$', 'ゆゆ式', '$20', 'hello20', '_', 'if'];
+            const results = [];
+            for (const word of words) {
+                expect(esutils.keyword.isIdentifierNameES5(word)).to.be.true;
+                results.push(expect(esutils.keyword.isIdentifierNameES6(word)).to.be.true);
+            }
+            return results;
+        });
+        it('returns false if provided string is not IdentifierName', function() {
+            const words = ['+hello', '0$', '-ゆゆ式', '#_', '_#'];
+            const results = [];
+            for (const word of words) {
+                expect(esutils.keyword.isIdentifierNameES5(word)).to.be.false;
+                results.push(expect(esutils.keyword.isIdentifierNameES6(word)).to.be.false);
+            }
+            return results;
+        });
+        it('returns false if provided an unmatched high surrogate', function () {
+            const words = ['\uD800a', '\uD800'];
+            const results = [];
+            for (const word of words) {
+                expect(esutils.keyword.isIdentifierNameES5(word)).to.be.false;
+                results.push(expect(esutils.keyword.isIdentifierNameES6(word)).to.be.false);
+            }
+            return results;
+        });
+        it('supports astral symbols', function() {
+            expect(esutils.keyword.isIdentifierNameES6('x\uDB40\uDDD5')).to.be.true;
+        });
+    });
+    describe('isIdentifierES5', function() {
+        it('returns false if provided string is empty', function() {
+            expect(esutils.keyword.isIdentifierES5('')).to.be.false;
+        });
+        it('returns true if provided string is Identifier', function() {
+            const words = ['hello', '$', 'ゆゆ式', '$20', 'hello20', '_'];
+            for (const word of words) {
+                expect(esutils.keyword.isIdentifierES5(word)).to.be.true;
+            }
+            expect(esutils.keyword.isIdentifierES5('yield', false)).to.be.true;
+            expect(esutils.keyword.isIdentifierES5('let', false)).to.be.true;
+        });
+        it('returns false if provided string is not Identifier', function() {
+            const words = ['+hello', '0$', '-ゆゆ式', '#_', '_#', 'if', 'null', 'true', 'false'];
+            for (const word of words) {
+                expect(esutils.keyword.isIdentifierES5(word)).to.be.false;
+            }
+            expect(esutils.keyword.isIdentifierES5('yield', true)).to.be.false;
+            expect(esutils.keyword.isIdentifierES5('let', true)).to.be.false;
+        });
+    });
+    describe('isIdentifierES6', function() {
+        it('returns false if provided string is empty', function() {
+            expect(esutils.keyword.isIdentifierES6('')).to.be.false;
+        });
+        it('returns true if provided string is Identifier', function() {
+            const words = ['hello', '$', 'ゆゆ式', '$20', 'hello20', '_'];
+            for (const word of words) {
+                expect(esutils.keyword.isIdentifierES6(word)).to.be.true;
+            }
+            expect(esutils.keyword.isIdentifierES6('let', false)).to.be.true;
+        });
+        it('returns false if provided string is not Identifier', function() {
+            const words = ['+hello', '0$', '-ゆゆ式', '#_', '_#', 'if', 'null', 'true', 'false'];
+            for (const word of words) {
+                expect(esutils.keyword.isIdentifierES6(word)).to.be.false;
+            }
+            expect(esutils.keyword.isIdentifierES6('yield', false)).to.be.false;
+            expect(esutils.keyword.isIdentifierES6('yield', true)).to.be.false;
+            expect(esutils.keyword.isIdentifierES6('let', true)).to.be.false;
+        });
+    });
+});
diff --git a/tools/generate-identifier-regex.js b/tools/generate-identifier-regex.js
index 2aef1f2..1dac1f6 100644
--- a/tools/generate-identifier-regex.js
+++ b/tools/generate-identifier-regex.js
@@ -1,14 +1,19 @@
 // Based on https://gist.github.com/mathiasbynens/6334847 by @mathias
 'use strict';
 
+const { writeFileSync } = require('fs');
+const { join } = require('path');
 const regenerate = require('regenerate');
 
 // Which Unicode version should be used?
-const version = '9.0.0';
+const pkg = require('../package.json');
+const dependencies = Object.keys(pkg.devDependencies);
+const unicodeDep = dependencies.find((name) => /^unicode-\d/.test(name));
+const [, version] = unicodeDep.match(/\D+(.+)$/);
 
 // Set up a shorthand function to import Unicode data.
 const get = function(what) {
-    return require('unicode-' + version + '/' + what + '/code-points');
+    return require(`unicode-${version}/${what}/code-points.js`);
 };
 
 // Get the Unicode categories needed to construct the ES5 regex.
@@ -35,8 +40,8 @@ const es5regexes = (function() { // ES 5.1
         .removeRange(0x010000, 0x10FFFF) // remove astral symbols
         .removeRange(0x00, 0x7F); // remove ASCII symbols (esutils-specific)
     return {
-        'NonAsciiIdentifierStart': '/' + identifierStart + '/',
-        'NonAsciiIdentifierPart': '/' + identifierPart + '/',
+        NonAsciiIdentifierStart: `/${identifierStart}/`,
+        NonAsciiIdentifierPart: `/${identifierPart}/`,
     };
 }());
 
@@ -59,29 +64,35 @@ const es6regexes = (function() {
         .removeRange(0x00, 0x7F); // remove ASCII symbols (esutils-specific)
 
     return {
-        'NonAsciiIdentifierStart': '/' + identifierStart + '/',
-        'NonAsciiIdentifierPart': '/' + identifierPart + '/',
+        NonAsciiIdentifierStart: `/${identifierStart}/`,
+        NonAsciiIdentifierPart: `/${identifierPart}/`,
     };
 }());
 
-console.log(
-    '// ECMAScript 5.1/Unicode v%s NonAsciiIdentifierStart:\n%s\n',
-    version,
-    es5regexes.NonAsciiIdentifierStart
-);
-console.log(
-    '// ECMAScript 5.1/Unicode v%s NonAsciiIdentifierPart:\n%s\n',
-    version,
-    es5regexes.NonAsciiIdentifierPart
-);
+writeFileSync(
+    join(__dirname, '../src/es5-identifier.js'),
+    `// DO NOT EDIT -- File auto-generated from /tools/generate-identifier-regex.js
+
+// ECMAScript 5.1/Unicode v${version} NonAsciiIdentifierStart:
+const NonAsciiIdentifierStart = ${es5regexes.NonAsciiIdentifierStart};
+
+// ECMAScript 5.1/Unicode v${version} NonAsciiIdentifierPart:
+const NonAsciiIdentifierPart = ${es5regexes.NonAsciiIdentifierPart};
 
-console.log(
-    '// ECMAScript 6/Unicode v%s NonAsciiIdentifierStart:\n%s\n',
-    version,
-    es6regexes.NonAsciiIdentifierStart
+export { NonAsciiIdentifierStart, NonAsciiIdentifierPart };
+`
 );
-console.log(
-    '// ECMAScript 6/Unicode v%s NonAsciiIdentifierPart:\n%s',
-    version,
-    es6regexes.NonAsciiIdentifierPart
+
+writeFileSync(
+    join(__dirname, '../src/es6-identifier.js'),
+    `// DO NOT EDIT -- File auto-generated from /tools/generate-identifier-regex.js
+
+// ECMAScript 6/Unicode v${version} NonAsciiIdentifierStart:
+const NonAsciiIdentifierStart = ${es6regexes.NonAsciiIdentifierStart};
+
+// ECMAScript 6/Unicode v${version} NonAsciiIdentifierPart:
+const NonAsciiIdentifierPart = ${es6regexes.NonAsciiIdentifierPart};
+
+export { NonAsciiIdentifierStart, NonAsciiIdentifierPart };
+`
 );