Rollup

Rollup is a JavaScript bundler specialized in creating reusable modules and optimized libraries. Unlike application-focused bundlers, Rollup natively leverages the ES modules (ESM) format to eliminate dead code through tree-shaking, producing extremely compact bundles. It has become the tool of choice for packaging npm libraries and modern frameworks.

Technical Fundamentals

• Static analysis of dependency graph based on ES6 imports/exports
• Native tree-shaking automatically eliminating unused code
• Multi-format output support (ESM, CommonJS, UMD, IIFE, AMD)
• Extensible plugin architecture compatible with Vite and WMR ecosystem

Strategic Benefits

• Bundles up to 50% lighter through efficient tree-shaking
• Readable output code facilitating production debugging
• Simultaneous generation of multiple formats for maximum compatibility
• Superior build performance for library-oriented projects
• Native integration with TypeScript and modern tooling
• Scope hoisting reducing final size and improving runtime execution

Practical Configuration Example

import resolve from '@rollup/plugin-node-resolve';
import commonjs from '@rollup/plugin-commonjs';
import typescript from '@rollup/plugin-typescript';
import terser from '@rollup/plugin-terser';

export default {
  input: 'src/index.ts',
  output: [
    {
      file: 'dist/bundle.esm.js',
      format: 'esm',
      sourcemap: true
    },
    {
      file: 'dist/bundle.cjs.js',
      format: 'cjs',
      sourcemap: true
    },
    {
      file: 'dist/bundle.umd.js',
      format: 'umd',
      name: 'MyLibrary',
      sourcemap: true,
      plugins: [terser()]
    }
  ],
  plugins: [
    resolve(),
    commonjs(),
    typescript({ tsconfig: './tsconfig.json' })
  ],
  external: ['react', 'react-dom']
};

Professional Implementation

1. Install Rollup and necessary plugins via npm/yarn/pnpm
2. Create rollup.config.js file defining entry points and output formats
3. Configure plugins for module resolution, transpilation, and minification
4. Declare external dependencies (peer dependencies) in 'external' field
5. Define package.json scripts for development and production builds
6. Enable sourcemaps to facilitate debugging
7. Test compatibility of generated bundles across different environments

Ecosystem and Related Tools

• @rollup/plugin-node-resolve - npm module resolution
• @rollup/plugin-commonjs - CJS to ESM conversion
• @rollup/plugin-typescript - Native TypeScript support
• @rollup/plugin-terser - Modern minification replacing UglifyJS
• rollup-plugin-visualizer - Visual bundle size analysis
• Vite - Framework using Rollup for production builds
• SWC/esbuild - High-performance alternatives for transpilation

Rollup has established itself as the industry standard for packaging reusable JavaScript libraries, offering an optimal balance between bundle size, performance, and code readability. Its adoption by major projects (Vue.js, Svelte, D3.js) and integration into Vite confirms its relevance in the modern ecosystem. For teams developing shared components or npm packages, Rollup guarantees optimized deliverables that minimize impact on consuming applications.