bun-hot-reloading

# Bun Hot Reloading Bun provides built-in hot reloading for faster development cycles. ## Watch Mode vs Hot Mode | Feature | `--watch` | `--hot` | |---------|-----------|---------| | Behavior | Restart process | Reload modules | | State | Lost on reload | Preserved | | Speed | ~20ms restart | Instant reload | | Use case | Any file type | Bun.serve HTTP | ## Watch Mode (--watch) Restarts the entire process when files change. ```bash # Basic watch mode bun --watch run src/index.ts # Watch specific script bun --watch run dev # Watch with test runner bun --watch test ``` ### package.json Scripts ```json { "scripts": { "dev": "bun --watch run src/index.ts", "dev:server": "bun --watch run src/server.ts", "test:watch": "bun --watch test" } } ``` ### Watch Behavior - Watches imported files automatically - Triggers on any `.ts`, `.tsx`, `.js`, `.jsx` change - Also watches `.json` imports - Restarts with fresh state ## Hot Mode (--hot) Reloads modules in-place without restarting the process. ```bash bun --hot run src/server.ts ``` ### HTTP Server Hot Reload ```typescript // src/server.ts let counter = 0; // State preserved across hot reloads export default { port: 3000, fetch(req: Request) { counter++; return new Response(`Request #${counter}`); }, }; ``` ```bash bun --hot run src/server.ts ``` When you modify `server.ts`, the module reloads instantly while `counter` keeps its value. ### Bun.serve with Hot Reload ```typescript // src/...