Skill

skills

Bun Runtime Modern JavaScript

Build high-performance JavaScript applications with Bun, the all-in-one runtime challenging Node.js. Native TypeScript support, built-in bundler, and 3x faster package installs.

JSONbored

October 23, 2025

2 views views

bun

runtime

javascript

typescript

performance

Skill Content

The main content for this skill.

bun-runtime-modern-javascript.txt

# Bun Runtime Modern JavaScript Skill

## What This Skill Enables

Claude can build and deploy JavaScript/TypeScript applications using Bun, the all-in-one JavaScript runtime that's 3x faster than Node.js for package installs and startup time. Bun includes a native bundler, test runner, package manager, and TypeScript transpiler in a single binary. From APIs to CLIs to build tools, Bun provides drop-in Node.js compatibility with modern performance.

## Prerequisites

**Required:**
- Claude Pro subscription or Claude Code CLI
- macOS, Linux, or WSL (Windows support in beta)
- curl or wget for installation
- Basic JavaScript/TypeScript knowledge

**What Claude handles automatically:**
- Writing Bun-optimized server code
- Configuring bun:test for testing
- Setting up Bun.serve() for HTTP servers
- Using Bun.build() for bundling
- Implementing file operations with Bun.file()
- Adding WebSocket support
- Configuring environment variables
- Optimizing for Bun's performance characteristics

## How to Use This Skill

### High-Performance HTTP Server

**Prompt:** "Create Bun HTTP server with: REST API routes, JSON parsing, CORS middleware, static file serving, WebSocket support, and error handling. Optimize for maximum req/sec."

Claude will:
1. Use Bun.serve() with fetch handler
2. Implement routing with URL patterns
3. Add CORS headers
4. Serve static files with Bun.file()
5. Set up WebSocket upgrade
6. Handle errors gracefully
7. Benchmark with wrk/autocannon

### CLI Tool Development

**Prompt:** "Build CLI tool with Bun for: file processing, progress bars, colored output, interactive prompts, and parallel operations. Package as standalone binary."

Claude will:
1. Parse args with Bun.argv
2. Use chalk for colors
3. Add ora for spinners
4. Implement inquirer prompts
5. Process files with Bun.file()
6. Use Bun.spawn() for parallel
7. Build executable with bun build

### Database Operations

**Prompt:** "Create Bun app with SQLite using bun:sqlite. Include: connection pooling, prepared statements, migrations, and query builder pattern."

Claude will:
1. Use bun:sqlite module
2. Set up connection pool
3. Create prepared statements
4. Implement migration system
5. Build query builder
6. Add transaction support
7. Handle errors and cleanup

### Testing with Bun

**Prompt:** "Set up Bun testing for API with: unit tests, integration tests, mocking, coverage reporting, and parallel execution."

Claude will:
1. Write tests with bun:test
2. Use expect assertions
3. Mock with spyOn
4. Configure coverage
5. Run tests in parallel
6. Add before/after hooks
7. Test HTTP endpoints

## Tips for Best Results

1. **Use Bun APIs**: Prefer `Bun.file()` over `fs`, `Bun.serve()` over http module. Bun's APIs are optimized and simpler.

2. **Native TypeScript**: No need for ts-node or build step. Bun runs TypeScript natively. Use .ts extensions directly.

3. **Built-in Bundler**: Use `bun build` instead of webpack/esbuild. Single-command bundling with tree-shaking.

4. **Fast Package Manager**: Run `bun install` instead of npm/pnpm. Uses global cache and parallel downloads.

5. **WebSocket Native**: Bun.serve() includes WebSocket upgrade. No need for ws or socket.io for simple cases.

## Common Workflows

### REST API Backend
```
"Build production REST API with Bun:
1. HTTP server with Bun.serve() and routing
2. JWT authentication middleware
3. Database with bun:sqlite or Postgres
4. Request validation with Zod
5. Rate limiting with in-memory store
6. File uploads with Bun.file()
7. WebSocket for real-time updates
8. Docker deployment with bun:alpine"
```

### Build Tool Development
```
"Create build tool with Bun:
1. File watching with Bun.watch()
2. Bundling with Bun.build()
3. TypeScript transpilation (automatic)
4. Minification and tree-shaking
5. Source maps generation
6. Plugin system for transforms
7. Parallel file processing
8. Cache invalidation"
```

### Microservices Infrastructure
```
"Build microservices with Bun:
1. Service discovery with etcd
2. gRPC communication
3. Health checks endpoint
4. Metrics collection
5. Structured logging
6. Graceful shutdown
7. Docker containers
8. Kubernetes deployment"
```

## Troubleshooting

**Issue:** "Node.js package not working in Bun"
**Solution:** Check Bun compatibility at bun.sh/docs. Most npm packages work. For native modules, ensure Bun version supports Node-API. Use --bun flag or check package.json engines field.

**Issue:** "Performance not better than Node.js"
**Solution:** Ensure using Bun APIs (Bun.serve not http). Check CPU-bound vs I/O-bound. Bun excels at I/O. Profile with bun:jsc. Verify using latest Bun version.

**Issue:** "TypeScript types not working"
**Solution:** Install @types packages with bun add -d. Check bunfig.toml has correct compilerOptions. Use bun-types for Bun APIs. Restart editor/LSP.

## Learn More

- [Bun Official Documentation](https://bun.sh/docs)
- [Bun GitHub Repository](https://github.com/oven-sh/bun)
- [Bun Discord Community](https://bun.sh/discord)
- [Awesome Bun Resources](https://github.com/apvarun/awesome-bun)

Features

Key capabilities and functionality

3x faster package installs with global cache
Native TypeScript support without transpilation
Built-in bundler, test runner, and package manager
Drop-in Node.js compatibility for most packages

Requirements

Prerequisites and dependencies

Bun 1.0+
macOS/Linux/WSL

Installation

Setup instructions and requirements

Claude Code Setup

Step 1: Run command

install-step-1.sh

bash

curl -fsSL https://bun.sh/install | bash

bun init (creates package.json)

bun add <packages> for dependencies

bun run --watch server.ts for dev mode

Claude Desktop Setup

Install Bun: curl -fsSL https://bun.sh/install | bash

Verify: bun --version

Ask Claude: 'Create Bun server for [your use case]'

Run with: bun run server.ts

Use Cases

Common scenarios and applications

High-performance HTTP servers with Bun.serve()
CLI tools with fast startup times
Build tools with native bundling

Troubleshooting

Common issues and solutions

npm package not compatible
Check bun.sh/docs for compatibility. Most packages work. For native modules, verify Bun version supports Node-API. Try --bun flag or update package.
Performance not improved over Node
Use Bun APIs (Bun.serve not http module). Bun excels at I/O-bound tasks. Profile with bun:jsc. Verify latest Bun version installed.
TypeScript types missing
Install @types packages: bun add -d @types/node. Add bun-types for Bun APIs. Check bunfig.toml compilerOptions. Restart LSP.

Usage Examples

Practical code examples demonstrating common use cases and implementation patterns

HTTP Server with Routing

http-server-with-routing.ts

typescript

const server = Bun.serve({
  port: 3000,
  async fetch(req) {
    const url = new URL(req.url);
    
    // Route handling
    if (url.pathname === '/') {
      return new Response('Hello from Bun!');
    }
    
    if (url.pathname === '/api/users') {
      const users = await getUsers();
      return Response.json(users);
    }
    
    // Static file serving
    if (url.pathname.startsWith('/static/')) {
      const file = Bun.file(`.${url.pathname}`);
      return new Response(file);
    }
    
    return new Response('Not Found', { status: 404 });
  },
});

console.log(`Listening on http://localhost:${server.port}`);

SQLite Database Operations

sqlite-database-operations.ts

typescript

import { Database } from 'bun:sqlite';

const db = new Database('mydb.sqlite');

// Create table
db.run(`
  CREATE TABLE IF NOT EXISTS users (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    name TEXT NOT NULL,
    email TEXT UNIQUE NOT NULL
  )
`);

// Prepared statement for insertion
const insert = db.prepare('INSERT INTO users (name, email) VALUES (?, ?)');
insert.run('Alice', 'alice@example.com');

// Query with prepared statement
const query = db.prepare('SELECT * FROM users WHERE id = ?');
const user = query.get(1);

console.log(user);

// Transaction
const insertMany = db.transaction((users) => {
  for (const user of users) {
    insert.run(user.name, user.email);
  }
});

insertMany([
  { name: 'Bob', email: 'bob@example.com' },
  { name: 'Charlie', email: 'charlie@example.com' },
]);

db.close();

Testing with bun:test

testing-with-bun-test.ts

typescript

import { expect, test, describe, beforeAll, afterAll } from 'bun:test';

describe('Math operations', () => {
  test('addition', () => {
    expect(1 + 1).toBe(2);
  });
  
  test('subtraction', () => {
    expect(5 - 3).toBe(2);
  });
});

describe('API tests', () => {
  let server;
  
  beforeAll(() => {
    server = Bun.serve({ port: 3001, fetch: () => new Response('OK') });
  });
  
  afterAll(() => {
    server.stop();
  });
  
  test('server responds', async () => {
    const res = await fetch('http://localhost:3001');
    expect(res.status).toBe(200);
    expect(await res.text()).toBe('OK');
  });
});

// Run with: bun test

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Skill

skills

Bun Runtime Modern JavaScript

Build high-performance JavaScript applications with Bun, the all-in-one runtime challenging Node.js. Native TypeScript support, built-in bundler, and 3x faster package installs.

JSONbored

October 23, 2025

2 views views

bun

runtime

javascript

typescript

performance

Skill Content

The main content for this skill.

bun-runtime-modern-javascript.txt

# Bun Runtime Modern JavaScript Skill

## What This Skill Enables

Claude can build and deploy JavaScript/TypeScript applications using Bun, the all-in-one JavaScript runtime that's 3x faster than Node.js for package installs and startup time. Bun includes a native bundler, test runner, package manager, and TypeScript transpiler in a single binary. From APIs to CLIs to build tools, Bun provides drop-in Node.js compatibility with modern performance.

## Prerequisites

**Required:**
- Claude Pro subscription or Claude Code CLI
- macOS, Linux, or WSL (Windows support in beta)
- curl or wget for installation
- Basic JavaScript/TypeScript knowledge

**What Claude handles automatically:**
- Writing Bun-optimized server code
- Configuring bun:test for testing
- Setting up Bun.serve() for HTTP servers
- Using Bun.build() for bundling
- Implementing file operations with Bun.file()
- Adding WebSocket support
- Configuring environment variables
- Optimizing for Bun's performance characteristics

## How to Use This Skill

### High-Performance HTTP Server

**Prompt:** "Create Bun HTTP server with: REST API routes, JSON parsing, CORS middleware, static file serving, WebSocket support, and error handling. Optimize for maximum req/sec."

Claude will:
1. Use Bun.serve() with fetch handler
2. Implement routing with URL patterns
3. Add CORS headers
4. Serve static files with Bun.file()
5. Set up WebSocket upgrade
6. Handle errors gracefully
7. Benchmark with wrk/autocannon

### CLI Tool Development

**Prompt:** "Build CLI tool with Bun for: file processing, progress bars, colored output, interactive prompts, and parallel operations. Package as standalone binary."

Claude will:
1. Parse args with Bun.argv
2. Use chalk for colors
3. Add ora for spinners
4. Implement inquirer prompts
5. Process files with Bun.file()
6. Use Bun.spawn() for parallel
7. Build executable with bun build

### Database Operations

**Prompt:** "Create Bun app with SQLite using bun:sqlite. Include: connection pooling, prepared statements, migrations, and query builder pattern."

Claude will:
1. Use bun:sqlite module
2. Set up connection pool
3. Create prepared statements
4. Implement migration system
5. Build query builder
6. Add transaction support
7. Handle errors and cleanup

### Testing with Bun

**Prompt:** "Set up Bun testing for API with: unit tests, integration tests, mocking, coverage reporting, and parallel execution."

Claude will:
1. Write tests with bun:test
2. Use expect assertions
3. Mock with spyOn
4. Configure coverage
5. Run tests in parallel
6. Add before/after hooks
7. Test HTTP endpoints

## Tips for Best Results

1. **Use Bun APIs**: Prefer `Bun.file()` over `fs`, `Bun.serve()` over http module. Bun's APIs are optimized and simpler.

2. **Native TypeScript**: No need for ts-node or build step. Bun runs TypeScript natively. Use .ts extensions directly.

3. **Built-in Bundler**: Use `bun build` instead of webpack/esbuild. Single-command bundling with tree-shaking.

4. **Fast Package Manager**: Run `bun install` instead of npm/pnpm. Uses global cache and parallel downloads.

5. **WebSocket Native**: Bun.serve() includes WebSocket upgrade. No need for ws or socket.io for simple cases.

## Common Workflows

### REST API Backend
```
"Build production REST API with Bun:
1. HTTP server with Bun.serve() and routing
2. JWT authentication middleware
3. Database with bun:sqlite or Postgres
4. Request validation with Zod
5. Rate limiting with in-memory store
6. File uploads with Bun.file()
7. WebSocket for real-time updates
8. Docker deployment with bun:alpine"
```

### Build Tool Development
```
"Create build tool with Bun:
1. File watching with Bun.watch()
2. Bundling with Bun.build()
3. TypeScript transpilation (automatic)
4. Minification and tree-shaking
5. Source maps generation
6. Plugin system for transforms
7. Parallel file processing
8. Cache invalidation"
```

### Microservices Infrastructure
```
"Build microservices with Bun:
1. Service discovery with etcd
2. gRPC communication
3. Health checks endpoint
4. Metrics collection
5. Structured logging
6. Graceful shutdown
7. Docker containers
8. Kubernetes deployment"
```

## Troubleshooting

**Issue:** "Node.js package not working in Bun"
**Solution:** Check Bun compatibility at bun.sh/docs. Most npm packages work. For native modules, ensure Bun version supports Node-API. Use --bun flag or check package.json engines field.

**Issue:** "Performance not better than Node.js"
**Solution:** Ensure using Bun APIs (Bun.serve not http). Check CPU-bound vs I/O-bound. Bun excels at I/O. Profile with bun:jsc. Verify using latest Bun version.

**Issue:** "TypeScript types not working"
**Solution:** Install @types packages with bun add -d. Check bunfig.toml has correct compilerOptions. Use bun-types for Bun APIs. Restart editor/LSP.

## Learn More

- [Bun Official Documentation](https://bun.sh/docs)
- [Bun GitHub Repository](https://github.com/oven-sh/bun)
- [Bun Discord Community](https://bun.sh/discord)
- [Awesome Bun Resources](https://github.com/apvarun/awesome-bun)

Features

Key capabilities and functionality

3x faster package installs with global cache
Native TypeScript support without transpilation
Built-in bundler, test runner, and package manager
Drop-in Node.js compatibility for most packages

Requirements

Prerequisites and dependencies

Bun 1.0+
macOS/Linux/WSL

Installation

Setup instructions and requirements

Claude Code Setup

Step 1: Run command

install-step-1.sh

bash

curl -fsSL https://bun.sh/install | bash

bun init (creates package.json)

bun add <packages> for dependencies

bun run --watch server.ts for dev mode

Claude Desktop Setup

Install Bun: curl -fsSL https://bun.sh/install | bash

Verify: bun --version

Ask Claude: 'Create Bun server for [your use case]'

Run with: bun run server.ts

Use Cases

Common scenarios and applications

High-performance HTTP servers with Bun.serve()
CLI tools with fast startup times
Build tools with native bundling

Troubleshooting

Common issues and solutions

npm package not compatible
Check bun.sh/docs for compatibility. Most packages work. For native modules, verify Bun version supports Node-API. Try --bun flag or update package.
Performance not improved over Node
Use Bun APIs (Bun.serve not http module). Bun excels at I/O-bound tasks. Profile with bun:jsc. Verify latest Bun version installed.
TypeScript types missing
Install @types packages: bun add -d @types/node. Add bun-types for Bun APIs. Check bunfig.toml compilerOptions. Restart LSP.

Usage Examples

Practical code examples demonstrating common use cases and implementation patterns

HTTP Server with Routing

http-server-with-routing.ts

typescript

const server = Bun.serve({
  port: 3000,
  async fetch(req) {
    const url = new URL(req.url);
    
    // Route handling
    if (url.pathname === '/') {
      return new Response('Hello from Bun!');
    }
    
    if (url.pathname === '/api/users') {
      const users = await getUsers();
      return Response.json(users);
    }
    
    // Static file serving
    if (url.pathname.startsWith('/static/')) {
      const file = Bun.file(`.${url.pathname}`);
      return new Response(file);
    }
    
    return new Response('Not Found', { status: 404 });
  },
});

console.log(`Listening on http://localhost:${server.port}`);

SQLite Database Operations

sqlite-database-operations.ts

typescript

import { Database } from 'bun:sqlite';

const db = new Database('mydb.sqlite');

// Create table
db.run(`
  CREATE TABLE IF NOT EXISTS users (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    name TEXT NOT NULL,
    email TEXT UNIQUE NOT NULL
  )
`);

// Prepared statement for insertion
const insert = db.prepare('INSERT INTO users (name, email) VALUES (?, ?)');
insert.run('Alice', 'alice@example.com');

// Query with prepared statement
const query = db.prepare('SELECT * FROM users WHERE id = ?');
const user = query.get(1);

console.log(user);

// Transaction
const insertMany = db.transaction((users) => {
  for (const user of users) {
    insert.run(user.name, user.email);
  }
});

insertMany([
  { name: 'Bob', email: 'bob@example.com' },
  { name: 'Charlie', email: 'charlie@example.com' },
]);

db.close();

Testing with bun:test

testing-with-bun-test.ts

typescript

import { expect, test, describe, beforeAll, afterAll } from 'bun:test';

describe('Math operations', () => {
  test('addition', () => {
    expect(1 + 1).toBe(2);
  });
  
  test('subtraction', () => {
    expect(5 - 3).toBe(2);
  });
});

describe('API tests', () => {
  let server;
  
  beforeAll(() => {
    server = Bun.serve({ port: 3001, fetch: () => new Response('OK') });
  });
  
  afterAll(() => {
    server.stop();
  });
  
  test('server responds', async () => {
    const res = await fetch('http://localhost:3001');
    expect(res.status).toBe(200);
    expect(await res.text()).toBe('OK');
  });
});

// Run with: bun test

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