(17) New exercise | Flatten

17_flatten/README.md

@@ -0,0 +1,11 @@
+# Exercise 17 - flatten
+
+Write a function that takes in an array of positive integers and an optional depth argument which defaults to `Infinity` if not specified.
+
+The function returns a new array with all sub-array elements concatenated into it recursively up to the specified depth.
+
+```javascript
+flatten([[1, 2], [3, 4]]); // Output: [1, 2, 3, 4]
+flatten([[1, [8, 9]], [3, 4]], 2); // Output: [1, [8, 9], 3, 4]
+flatten([2, 4, 6]); // Output: [2, 4, 6]
+```

17_flatten/flatten.js

@@ -0,0 +1,6 @@
+const flatten = function() {
+
+};
+
+// Do not edit below this line
+module.exports = flatten;

17_flatten/flatten.spec.js

@@ -0,0 +1,15 @@
+const flatten = require('./flatten');
+
+describe('flatten', () => {
+  test('First test description', () => {
+    // Replace this comment with any other necessary code, and update the expect line as necessary
+
+    expect(flatten()).toBe('');
+  });
+
+  test.skip('Second test description', () => {
+    // Replace this comment with any other necessary code, and update the expect line as necessary
+
+    expect(flatten()).toBe('');
+  });
+});

17_flatten/solution/flatten-solution.js

@@ -0,0 +1,13 @@
+const flatten = function (array, depth = Infinity) {
+  if (depth === 0 || !array.some(Array.isArray)) return array
+
+  let flattened = []
+  array.forEach(el => {
+   flattened = flattened.concat(el) 
+  });
+
+  return flatten(flattened, depth - 1)
+} 
+
+// Do not edit below this line
+module.exports = flatten;

17_flatten/solution/flatten-solution.spec.js

@@ -0,0 +1,17 @@
+const flatten = require('./flatten-solution');
+
+describe('flatten', () => {
+  test('Works', () => {
+    expect(flatten([[1, [2, 3]], 4], 1)).toEqual([1, [2, 3], 4])
+  })
+  test('Works with a depth argument', () => {
+    expect(flatten([ [1, 2], [3, 4, [[1, [8, 9]], [3, 4]], 2] ], 2)).toEqual([1, 2, 3, 4, [1, [ 8, 9 ]], [3, 4], 2]);
+  });
+
+  test('Works with no depth argument', () => {
+    expect(flatten([[[1, 2], [3, 4]], 1, [[[[[[[[1]]]]], 4, [[[[[[5, 4]]]]]], 1]]]])).toEqual([1, 2, 3, 4, 1, 1, 4, 5, 4, 1]);
+  });
+  test('Works with an empty array', () => {
+    expect(flatten([])).toEqual([]);
+  });
+});