bun-dev-server

Included with Lifetime

$97 forever

Set up high-performance development servers with Hot Module Replacement. Use when creating dev servers for web apps, setting up React Fast Refresh, or configuring API servers with live reload.

Web Dev

What this skill does


# Bun Development Server Setup

You are assisting with setting up a high-performance development server using Bun.serve with Hot Module Replacement (HMR) and React Fast Refresh.

## Workflow

### 1. Determine Server Type

Ask the user what type of development server they need:

- **React/Frontend App**: SPA with React Fast Refresh
- **API Server**: REST/GraphQL API with auto-reload
- **Full-Stack App**: Frontend + API combined
- **Static Server**: File server with live reload

### 2. Check Prerequisites

```bash
# Verify Bun installation
bun --version

# Check if project has package.json
ls -la package.json
```

If no package.json exists, suggest running `bun init` first.

### 3. Install Dependencies

**For React Apps:**
```bash
bun add react react-dom
bun add -d @types/react @types/react-dom
```

**For API with Hono (recommended):**
```bash
bun add hono
```

**For Full-Stack:**
```bash
bun add react react-dom hono
bun add -d @types/react @types/react-dom
```

### 4. Create Server Configuration

#### React Development Server

Create `server.ts` in the project root:

```typescript
import type { ServerWebSocket } from "bun";

const clients = new Set<ServerWebSocket<unknown>>();

const server = Bun.serve({
  port: 3000,

  async fetch(request, server) {
    const url = new URL(request.url);

    // WebSocket for HMR
    if (url.pathname === "/_hmr") {
      const upgraded = server.upgrade(request);
      if (upgraded) return undefined;
      return new Response("WebSocket upgrade failed", { status: 500 });
    }

    // Serve index.html for SPA routing
    if (url.pathname === "/" || !url.pathname.includes(".")) {
      return new Response(
        Bun.file("public/index.html"),
        { headers: { "Content-Type": "text/html" } }
      );
    }

    // Serve static files
    const filePath = `public${url.pathname}`;
    const file = Bun.file(filePath);

    if (await file.exists()) {
      return new Response(file);
    }

    return new Response("Not Found", { status: 404 });
  },

  websocket: {
    open(ws) {
      clients.add(ws);
      console.log("HMR client connected");
    },

    close(ws) {
      clients.delete(ws);
      console.log("HMR client disconnected");
    },

    message(ws, message) {
      // Handle client messages if needed
    },
  },
});

console.log(`🚀 Dev server running at http://localhost:${server.port}`);

// Watch for file changes
const watcher = Bun.file.watch(import.meta.dir + "/src", {
  recursive: true,
});

for await (const event of watcher) {
  if (event.kind === "change" && event.path.endsWith(".tsx")) {
    console.log(`📝 File changed: ${event.path}`);

    // Notify all connected clients to reload
    for (const client of clients) {
      client.send(JSON.stringify({ type: "reload" }));
    }
  }
}
```

Create `public/index.html`:

```html
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Bun + React App</title>
</head>
<body>
  <div id="root"></div>
  <script type="module" src="/src/index.tsx"></script>

  <!-- HMR Client -->
  <script>
    const ws = new WebSocket('ws://localhost:3000/_hmr');

    ws.addEventListener('message', (event) => {
      const data = JSON.parse(event.data);

      if (data.type === 'reload') {
        console.log('🔄 Reloading...');
        window.location.reload();
      }
    });

    ws.addEventListener('close', () => {
      console.log('❌ HMR connection lost. Reconnecting...');
      setTimeout(() => window.location.reload(), 1000);
    });
  </script>
</body>
</html>
```

Create `src/index.tsx`:

```typescript
import { render } from 'react-dom';
import App from './App';

const root = document.getElementById('root');
render(<App />, root);
```

Create `src/App.tsx`:

```typescript
export default function App() {
  return (
    <div>
      <h1>Welcome to Bun + React!</h1>
      <p>Edit src/App.tsx to see HMR in action</p>
    </div>
  );
}
```

#### API Server with Hono

Create `server.ts`:

```typescript
import { Hono } from 'hono';
import { cors } from 'hono/cors';
import { logger } from 'hono/logger';

const app = new Hono();

// Middleware
app.use('*', cors());
app.use('*', logger());

// Routes
app.get('/', (c) => {
  return c.json({ message: 'Welcome to Bun API' });
});

app.get('/api/health', (c) => {
  return c.json({ status: 'ok', timestamp: Date.now() });
});

// Example POST endpoint
app.post('/api/users', async (c) => {
  const body = await c.req.json();
  return c.json({ created: true, data: body }, 201);
});

// Start server
const server = Bun.serve({
  port: process.env.PORT || 3000,
  fetch: app.fetch,
});

console.log(`🚀 API server running at http://localhost:${server.port}`);
```

#### Full-Stack Server

Create `server.ts`:

```typescript
import { Hono } from 'hono';
import { serveStatic } from 'hono/bun';

const app = new Hono();

// API routes
const api = new Hono();

api.get('/health', (c) => c.json({ status: 'ok' }));
api.get('/users', (c) => c.json({ users: [] }));

app.route('/api', api);

// Serve static files
app.use('/*', serveStatic({ root: './public' }));

// SPA fallback
app.get('*', (c) => c.html(Bun.file('public/index.html')));

const server = Bun.serve({
  port: 3000,
  fetch: app.fetch,
});

console.log(`🚀 Full-stack server at http://localhost:${server.port}`);
```

### 5. Configure React Fast Refresh (Advanced)

For true React Fast Refresh, create `hmr-runtime.ts`:

```typescript
// React Fast Refresh runtime
let timeout: Timer | null = null;

export function refresh() {
  if (timeout) clearTimeout(timeout);

  timeout = setTimeout(() => {
    // Re-import the App component
    import('./App.tsx?t=' + Date.now()).then((module) => {
      const { render } = require('react-dom');
      const root = document.getElementById('root');
      render(module.default(), root);
    });
  }, 100);
}

// Listen for HMR events
if (import.meta.hot) {
  import.meta.hot.accept(() => {
    refresh();
  });
}
```

### 6. Environment Configuration

Create `.env.development`:

```bash
# Server
PORT=3000
NODE_ENV=development

# API
API_URL=http://localhost:3000/api

# Features
ENABLE_HMR=true
```

Create `.env.production`:

```bash
# Server
PORT=8080
NODE_ENV=production

# API
API_URL=https://api.example.com

# Features
ENABLE_HMR=false
```

Load environment in `server.ts`:

```typescript
// Environment is loaded automatically by Bun
const isDev = process.env.NODE_ENV === 'development';
const port = process.env.PORT || 3000;
```

### 7. Update package.json Scripts

Add development scripts:

```json
{
  "scripts": {
    "dev": "bun run --hot server.ts",
    "dev:watch": "bun run --watch server.ts",
    "start": "NODE_ENV=production bun run server.ts",
    "build": "bun build src/index.tsx --outdir=dist --minify",
    "clean": "rm -rf dist"
  }
}
```

**Script explanations:**
- `dev`: Run with hot reload (restarts on file changes)
- `dev:watch`: Watch mode (faster, but doesn't reload on crash)
- `start`: Production mode
- `build`: Build frontend for production

### 8. Configure TypeScript

Update `tsconfig.json`:

```json
{
  "compilerOptions": {
    "target": "ES2022",
    "lib": ["ES2022", "DOM", "DOM.Iterable"],
    "module": "ESNext",
    "moduleResolution": "bundler",
    "jsx": "react-jsx",
    "types": ["bun-types"],
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true,
    "resolveJsonModule": true,
    "allowImportingTsExtensions": true,
    "noEmit": true,
    "paths": {
      "@/*": ["./src/*"]
    }
  },
  "include": ["src/**/*", "server.ts"]
}
```

### 9. Create Project Structure

Generate complete project structure:

```
project/
├── server.ts              # Development server
├── src/
│   ├── index.tsx         # App entry point
│   ├── App.tsx           # Main component
│   ├── components/       # React components
│   └── styles/           # CSS files
├── public/
│   ├── index.html        # HTML template
│   └── assets/           # Sta

Files: 2

Size: 20.2 KB

Complexity: 38/100

Category: Web Dev

Source: https://github.com/daleseo/bun-skills/tree/main/skills/bun-dev-server

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