bun

bun Best Practices

Bun is our go-to runtime for high-performance JavaScript/TypeScript backend services. It's an all-in-one toolkit designed for speed and developer experience. Adhere to these guidelines to maximize Bun's potential and maintain code quality.

1. Embrace Bun's Integrated Toolchain

Bun's strength lies in its unified toolchain. Always default to Bun's built-in features over external alternatives unless a specific project requirement dictates otherwise.

✅ GOOD: Use Bun's native tools

• Package Management: bun install for dependencies, bun add for new packages.
• Bundling: bun build for zero-config bundling and standalone executables.
• Testing: bun test for Jest-compatible testing, including watch mode and coverage.
• Runtime: bun run or bun <file> for execution.

# Install dependencies (faster than npm/yarn)
bun install

# Add a new package
bun add zod

# Run tests
bun test --coverage

# Build for deployment (e.g., a serverless function)
bun build ./src/index.ts --target=bun --outfile=./dist/server

❌ BAD: Mixing package managers or external bundlers unnecessarily

Avoid npm install or yarn add in Bun projects. Don't use Webpack or Rollup if bun build suffices.

2. Modern JavaScript Language Features

Always use current ECMAScript features (ES2015+). This improves readability, reduces bugs, and aligns with modern development.

✅ GOOD: Modern JS syntax

// 1. Prefer `const` and `let` over `var`
const API_URL = 'https://api.example.com';
let retryCount = 0;

// 2. Use ES Modules for all imports/exports
import { serve } from 'bun'; // Bun's native HTTP server
import { z } from 'zod';

// 3. Use Classes for object-oriented patterns
class UserService {
  #users = new Map(); // 4. Private class fields for true encapsulation

  constructor() {
    this.#users.set('1', { id: '1', name: 'Alice' });
  }

  // 5. Arrow functions for methods to preserve `this` context
  getUser = (id) => {
    return this.#users.get(id);
  };
}

// 6. Nullish coalescing (??) for default values
const user = new UserService().getUser('2');
const userName = user?.name ?? 'Guest'; // 7. Optional chaining (?.) for safe property access

// 8. Async/await for asynchronous operations
async function fetchData(url) {
  try {
    const response = await fetch(url);
    if (!response.ok) {
      throw new Error(`HTTP error! Status: ${response.status}`);
    }
    return await response.json();
  } catch (error) {
    console.error('Failed to fetch:', error);
    return null;
  }
}

// 9. Use `Map` for key-value pairs where keys aren't always strings or order matters
const configMap = new Map([
  ['port', 3000],
  ['debugMode', true],
]);

// 10. Reliable Array checks
const data = [];
if (Array.isArray(data)) {
  console.log('Data is an array.');
}