diff --git a/implement-shell-tools/cat/my_cat.js b/implement-shell-tools/cat/my_cat.js
new file mode 100644
index 00000000..b23b575f
--- /dev/null
+++ b/implement-shell-tools/cat/my_cat.js
@@ -0,0 +1,45 @@
+import { promises as fs } from 'node:fs';
+import { argv } from 'node:process';
+
+const args = argv.slice(2); // skip node and script name
+
+let showLineNumb = false;
+let showNoBlankNumb = false
+const files = [];
+
+
+args.forEach(arg => {
+  if (arg === '-n') {
+    showLineNumb = true;
+  } else if (arg === '-b') {
+    showNoBlankNumb = true;
+  }else {  
+    files.push(arg); 
+  }
+});
+
+if (files.length === 0) {
+  console.error('No input file specified');
+  process.exit(1);
+}
+
+// Global counters across all files
+let counter = 1;
+
+for (const file of files) {
+  try {
+    let content = await fs.readFile(file, 'utf-8');
+    const lines = content.split('\n');
+
+    if (showNoBlankNumb) {     // Number only non-blank lines
+        content = lines.map(line => 
+          line.trim() === '' ? '' : `${counter++}\t${line}`
+        ).join('\n');
+    } else if (showLineNumb) {  // Number all lines
+        content = lines.map((line) => `${counter++}\t${line}`).join('\n');
+    }
+    console.log(content);
+  } catch (err) {
+  console.error(`Cannot access '${file}': ${err.message}`);
+  }
+}
\ No newline at end of file
diff --git a/implement-shell-tools/ls/my_ls.js b/implement-shell-tools/ls/my_ls.js
new file mode 100644
index 00000000..558499ba
--- /dev/null
+++ b/implement-shell-tools/ls/my_ls.js
@@ -0,0 +1,32 @@
+import { readdirSync } from 'node:fs';
+import { argv } from 'node:process';
+
+const args = argv.slice(2); // skips node and script name
+
+const flags = args.filter(arg => arg.startsWith('-'));
+const operands = args.filter(arg => !arg.startsWith('-'));
+
+let showAll = flags.includes('-a');
+let onePerLine = flags.includes('-1');
+
+if (operands.length === 0) operands.push('.'); // defaults to current dir
+
+operands.forEach(dir => {
+  try {
+    let files = readdirSync(dir);  // Reads the contents of the dir synchronously (readdirSync)
+
+    if (!showAll) {
+      files = files.filter(file => !file.startsWith('.'));
+    }
+
+    files.sort((a, b) => a.localeCompare(b));
+
+    if (onePerLine) {
+      files.forEach(file => console.log(file));
+    } else {
+      console.log(files.join('   '));
+    }
+  } catch (err) {
+    console.error(`ls: cannot access '${dir}': ${err.message}`);
+  }
+});
\ No newline at end of file
diff --git a/implement-shell-tools/wc/my_wc.js b/implement-shell-tools/wc/my_wc.js
new file mode 100644
index 00000000..35c77e32
--- /dev/null
+++ b/implement-shell-tools/wc/my_wc.js
@@ -0,0 +1,96 @@
+import { promises as fs } from 'node:fs';
+import { argv } from 'node:process';
+
+const args = argv.slice(2);
+
+if (args.length === 0) {
+  console.error('Usage: node my_wc.mjs [-l] [-w] [-c] <file> [file2 ...]');
+  process.exit(1);
+}
+
+// Parse flags and files
+const flags = {
+  l: false,
+  w: false,
+  c: false,
+};
+
+const files = [];
+
+for (const arg of args) {
+  if (arg.startsWith('-') && arg.length > 1) {
+    for (const ch of arg.slice(1)) {
+      if (flags.hasOwnProperty(ch)) {
+        flags[ch] = true;
+      } else {
+        console.error(`Unknown option: -${ch}`);
+        process.exit(1);
+      }
+    }
+  } else {
+    files.push(arg);
+  }
+}
+
+if (files.length === 0) {
+  console.error('Error: no files specified.');
+  process.exit(1);
+}
+
+// If no flags specified, show all by default
+const showLines = flags.l || (!flags.l && !flags.w && !flags.c);
+const showWords = flags.w || (!flags.l && !flags.w && !flags.c);
+const showBytes = flags.c || (!flags.l && !flags.w && !flags.c);
+
+function pad(num, width = 8) {
+  return num.toString().padStart(width, ' ');
+}
+
+function formatOutput({ lines, words, bytes }, label) {
+  let output = '';
+  if (showLines) output += pad(lines);
+  if (showWords) output += pad(words);
+  if (showBytes) output += pad(bytes);
+  output += ` ${label}`;
+  return output;
+}
+
+async function countFile(file) {
+  try {
+    const content = await fs.readFile(file, 'utf-8');
+    const lines = content.split('\n').length - 1;
+    const words = content.trim().split(/\s+/).filter(Boolean).length;
+    const bytes = Buffer.byteLength(content, 'utf-8');
+
+    const counts = { lines, words, bytes };
+    console.log(formatOutput(counts, file));
+
+    return counts;
+  } catch (err) {
+    console.error(`Cannot access '${file}': ${err.message}`);
+    return null;
+  }
+}
+
+async function main() {
+  // Instead of .map, I can explicitly collect promises using forEach():
+  const promises = [];
+  files.forEach(file => {
+    promises.push(countFile(file));
+  });
+  const counts = await Promise.all(promises);
+
+  const validCounts = counts.filter(c => c !== null);
+
+  if (validCounts.length > 1) {
+    const totals = {
+      lines: validCounts.reduce((sum, c) => sum + c.lines, 0),
+      words: validCounts.reduce((sum, c) => sum + c.words, 0),
+      bytes: validCounts.reduce((sum, c) => sum + c.bytes, 0),
+    }
+
+    console.log(formatOutput(totals, 'total'));
+  }
+}
+
+main();