bun-runtime

# Bun Runtime Bun is a fast all-in-one JavaScript runtime built on JavaScriptCore (Safari's engine). It provides 4x faster startup than Node.js on Linux. ## Quick Start ```bash # Run a file bun run index.ts bun index.ts # shorthand # Run with watch mode bun --watch run index.ts # Run package.json script bun run dev # Run with hot reloading bun --hot run server.ts ``` ## Core CLI Flags | Flag | Purpose | |------|---------| | `--watch` | Restart on file changes | | `--hot` | Hot module replacement (preserves state) | | `--smol` | Reduce memory usage (slower GC) | | `--inspect` | Enable debugger | | `--preload` | Load modules before execution | | `--env-file` | Load specific .env file | | `-e, --eval` | Evaluate code string | ## Running Files Bun transpiles TypeScript and JSX on-the-fly: ```bash bun run index.js bun run index.ts bun run index.jsx bun run index.tsx ``` **Important**: Put Bun flags immediately after `bun`: ```bash bun --watch run dev # Correct bun run dev --watch # Wrong - flag passed to script ``` ## Package.json Scripts ```bash # Run script bun run dev bun dev # shorthand (if no Bun command conflicts) # List available scripts bun run # Run with Bun instead of Node bun run --bun vite ``` Bun respects lifecycle hooks (`preclean`, `postclean`, etc.). ## Watch Mode vs Hot Reloading | Mode | Flag | Behavior | |------|------|----------| | Watch | `--watch` | Full process restart on changes | | Hot | `--hot` | Replace modules, preserve state ...