Which bundler should I use for ES Modules?

Top choices: 1) Vite - Fast, modern, ESM-first with instant HMR (recommended for new projects), 2) Webpack - Mature, extensive plugin ecosystem, handles complex builds, 3) Rollup - Excellent for libraries, great tree-shaking, 4) esbuild - Extremely fast, minimal config, 5) Parcel - Zero-config option. Choose based on project needs: Vite for apps, Rollup for libraries, Webpack for complex requirements.

Do I need TypeScript with ES Modules?

TypeScript is optional but highly recommended. Benefits: 1) Type safety catches errors early, 2) Better IDE support with autocomplete, 3) Refactoring confidence, 4) Self-documenting code. TypeScript compiles to JavaScript and works seamlessly with ES Modules. Modern tools like Vite and esbuild have built-in TypeScript support with no config needed.

How do I test ES Modules?

Testing options: 1) Vitest - Fast, Vite-powered, native ESM support, 2) Jest with experimental ESM mode, 3) Node.js native test runner with --experimental-test-coverage, 4) Mocha/Chai with ESM loader. Vitest is recommended for new projects - it's fast, has great DX, and works with ES Modules out of the box. Configure with 'type': 'module' in package.json.

What is Vite and why is it popular?

Vite is a modern build tool that leverages native ES Modules for instant dev server startup and lightning-fast HMR. Instead of bundling everything in dev, it serves modules individually using the browser's native import. In production, it uses Rollup for optimized bundles. Benefits: near-instant server start, instant HMR, optimized production builds, and great DX with minimal config.

ES Modules Tooling & Ecosystem

Vite

Lightning-fast development server leveraging native ES Modules with instant HMR.

npm create vite@latest my-app
cd my-app && npm install && npm run dev

Key Features:

No bundling in dev mode (native ESM)
Instant server start
Lightning fast HMR
Production builds with Rollup

Webpack

Powerful module bundler with extensive plugin ecosystem.

// webpack.config.js
export default {
  entry: './src/index.js',
  output: { filename: 'bundle.js' },
  module: {
    rules: [
      { test: /\.js$/, use: 'babel-loader' }
    ]
  }
};

Rollup

Optimized for library bundling with excellent tree-shaking.

// rollup.config.js
export default {
  input: 'src/index.js',
  output: {
    file: 'dist/bundle.js',
    format: 'esm'
  }
};

TypeScript

Full support for ES Modules with type checking.

// tsconfig.json
{
  "compilerOptions": {
    "module": "ESNext",
    "target": "ESNext",
    "moduleResolution": "bundler"
  }
}

ESLint

Lint ES Modules with proper import/export validation.

{
  "parserOptions": { "sourceType": "module" },
  "plugins": ["import"],
  "rules": {
    "import/no-unresolved": "error"
  }
}

CDNs

Load ES Modules directly from CDNs without build steps.

esm.sh

import React from 'https://esm.sh/react'

Skypack

import lodash from 'https://cdn.skypack.dev/lodash'

Tooling & Ecosystem