esm-dev/esm.sh
Esm.sh
esm.sh is a proxy-based registry and distribution system for buildless web development. It retrieves packages from external registries and serves them as ES modules directly to the browser, eliminating the need for a local build step.
The project transforms TypeScript, JSX, TSX, and Vue files into browser-compatible JavaScript on the fly during the request process. It handles Node.js built-in resolution by mapping internal modules to browser-compatible polyfills and manages dependency versioning and aliasing through URL query parameters.
The system optimizes delivery via request-time tree shaking to remove unused code and can bundle a module with its external dependencies into a single file. Additionally, it provides mechanisms for bootstrapping and executing JavaScript modules within a web worker context.
Features
- ES Module Registry Proxies - Acts as a proxy-based registry that retrieves packages from external sources and serves them as ES modules.
- On-the-Fly Module Transpilers - Converts TypeScript, Vue, and Svelte files into browser-compatible JavaScript modules on the fly during the request process.
- Query-Based Resolution - Determines module versions and aliases by parsing query parameters within the request URL.
- Dependency Aliasing - Provides control over module versions and aliases using URL query parameters.
- HTTP Module Distribution - Serves JavaScript modules from external registries as URLs to enable browser-side loading.
- Just-In-Time Module Compilation - Compiles TypeScript and Vue files into browser-compatible JavaScript on the fly during the request process.
- TypeScript Execution - Provides native execution of TypeScript, JSX, and TSX by compiling them on the fly.
- Node.js Core Shims - Maps Node.js built-in modules to compatible versions for use in browser environments.
- NPM Module Compatibility - Imports and resolves NPM packages as ES modules via URLs for use in web applications.
- Buildless - Enables loading JavaScript modules from registries directly in the browser to eliminate the need for a local build step.
- Node.js Browser Emulation - Provides mechanisms to execute Node.js core modules within web browsers via compatible polyfills.
- Dependency Bundling - Packages a module and its external dependencies into a single JavaScript file to reduce network requests.
- In-Browser Script Compilers - Compiles TypeScript, JSX, and TSX code written inside HTML script tags for immediate browser execution.
- Web Worker Execution - Wraps module code with a custom loader to execute JavaScript within a web worker context.
- Bundle Optimizers - Reduces the amount of code sent to the browser through request-time tree shaking and dependency bundling.
- Tree-Shaking Optimizations - Removes unused exports from modules to optimize bundle size and reduce the payload sent to the browser.
- Tree-Shaking Optimizers - Analyzes module exports during the fetch process to remove unused code and reduce payload size.
