What's the main difference between ES Modules and CommonJS?

Key differences: 1) Syntax - ESM uses import/export vs CommonJS require()/module.exports, 2) Loading - ESM is asynchronous and static, CommonJS is synchronous and dynamic, 3) Browser support - ESM works natively in browsers, CommonJS doesn't, 4) Tree-shaking - ESM enables it, CommonJS doesn't, 5) Binding - ESM exports are live references, CommonJS exports are copies. ESM is the modern standard.

Should I use Webpack, Rollup, or Vite?

Choose based on needs: Vite - best for modern web apps, instant dev server, minimal config. Webpack - mature, handles complex builds, extensive plugins, good for large apps with special requirements. Rollup - ideal for libraries, excellent tree-shaking, smaller output. esbuild/Parcel - fastest builds, good for simple projects. For most new projects, start with Vite.

Which browsers support ES Modules?

All modern browsers support ES Modules: Chrome 61+ (2017), Firefox 60+ (2018), Safari 11+ (2017), Edge 16+ (2017). This covers 95%+ of users globally. For older browser support, use a bundler with transpilation (Babel). You can use script type='module' for modern browsers and script nomodule as a fallback for older ones.

What are the advantages of ES Modules over older module systems?

ES Modules advantages: 1) Official JavaScript standard, not a third-party solution, 2) Native browser support without bundlers, 3) Static structure enables tree-shaking and better optimization, 4) Async loading by design, 5) Cleaner syntax, 6) Live bindings for dynamic updates, 7) Better for code splitting, 8) Works across browsers and Node.js. It's the future of JavaScript modularity.

ES Modules Comparison Tables

ES Modules vs CommonJS

Feature	ES Modules (ESM)	CommonJS (CJS)
Syntax	`import / export`	`require() / module.exports`
Loading	Asynchronous	Synchronous
Tree-shaking	✅ Yes	❌ No (limited)
Live Bindings	✅ Yes	❌ No (copy)
Dynamic imports	✅ `import()`	⚠️ `require()` (sync only)
Browser support	✅ Native	❌ Requires bundler
Node.js support	✅ v12.17+ (stable v14+)	✅ Default before v13
Top-level await	✅ Yes	❌ No
File extension	`.js` (with `"type": "module"`) or `.mjs`	`.js` (default) or `.cjs`
Circular dependencies	✅ Better handling	⚠️ Can cause issues
Standard	✅ ECMAScript standard	⚠️ Node.js specific
Recommended for	Modern projects, browsers, full-stack	Legacy Node.js projects

Bundler Comparison

Feature	Vite	Webpack	Rollup	esbuild
Dev Server Speed	⚡ Instant	🐌 Slow	🐌 Slow	⚡ Very Fast
Build Speed	Fast (Rollup)	Moderate	Moderate	Extremely Fast
HMR	✅ Instant	✅ Good	⚠️ Plugin-based	❌ Limited
Configuration	Minimal	Complex	Moderate	Minimal
Plugin Ecosystem	Mature	Massive	Mature	Limited
Tree-shaking	✅ Excellent	✅ Good	✅ Excellent	✅ Good
Code Splitting	✅ Automatic	✅ Advanced	✅ Manual	⚠️ Basic
Framework Support	React, Vue, Svelte	All frameworks	Library-focused	Basic
Learning Curve	Easy	Steep	Moderate	Easy
Best For	Modern SPAs, DX	Complex apps, legacy	Libraries, production	Speed, simple builds

Next-Generation Bundlers

Tool	Speed	ESM Support	Tree-shaking	Config
Rspack	Very Fast (23x webpack)	Full	Yes	webpack-compatible
Turbopack	Very Fast	Full	Yes	Next.js native
Rolldown	Very Fast (Rust)	Full	Yes	Rollup-compatible
Bun	Very Fast (Zig)	Full	Yes	Minimal

JavaScript Runtimes

Runtime ESM Comparison

Feature	Node.js 22+	Deno 2.x	Bun 1.3+
ESM Default	With "type": "module"	Yes (native)	Yes (native)
CJS Support	Full	Via npm compat	Full interop
require(esm)	Node 23+ default	N/A	Always worked
TypeScript	Type stripping (24+)	Native	Native
Import Maps	--experimental	deno.json	bunfig.toml
Import Attributes	Stable	Stable	Stable

Browser Support

Browser	ES Modules	Dynamic Import	Import Maps	Top-Level Await
Chrome	✅ 61+	✅ 63+	✅ 89+	✅ 89+
Firefox	✅ 60+	✅ 67+	✅ 108+	✅ 89+
Safari	✅ 11+	✅ 11.1+	✅ 16.4+	✅ 15+
Edge	✅ 79+	✅ 79+	✅ 89+	✅ 89+
Opera	✅ 48+	✅ 50+	✅ 75+	✅ 75+
iOS Safari	✅ 11+	✅ 11.3+	✅ 16.4+	✅ 15+
Chrome Android	✅ 61+	✅ 63+	✅ 89+	✅ 89+

Note: ES Modules have excellent browser support. Over 95% of users globally have browsers that support ES Modules. For legacy browsers, use bundlers with transpilation.

Module Format Comparison

Format	Full Name	Environment	Status
ESM	ES Modules	Browser + Node.js	✅ Modern Standard
CJS	CommonJS	Node.js	⚠️ Legacy (widely used)
UMD	Universal Module Definition	Browser + Node.js	⚠️ Legacy (compatibility)
AMD	Asynchronous Module Definition	Browser (RequireJS)	❌ Deprecated
IIFE	Immediately Invoked Function Expression	Browser	⚠️ Simple use cases
System	SystemJS	Browser	⚠️ Polyfill/loader

Comparison Tables