Bun - Ultra-fast JavaScript Runtime
Bun is a modern JavaScript runtime like Node.js, but it's designed to be much faster and more efficient.
GitHub
https://github.com/oven-sh/bun
What is Bun?
Bun is a drop-in replacement for Node.js that includes:
All in a single executable!
Key Features
1. Lightning Fast
2. All-in-One
3. Modern Features
4. Developer Experience
Installation
macOS & Linux
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curl -fsSL https://bun.sh/install | bash
Windows
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powershell -c "irm bun.sh/install.ps1|iex"
Using npm
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npm install -g bun
Quick Start
Hello World
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javascript
// server.js
Bun.serve({
port: 3000,
fetch(req) {
return new Response("Hello Bun!");
},
});
console.log("Listening on http://localhost:3000");
Run it:
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bun run server.js
Package Manager
Install Packages
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# Install dependencies
bun install
# Add package
bun add react
# Add dev dependency
bun add -D typescript
# Remove package
bun remove react
Speed Comparison
| Operation | Bun | npm/pnpm | Speedup |
|-----------|-----|----------|---------|
| Install 1000 packages | 1.2s | 15s | 12x |
| Install 1 package | 0.02s | 1.2s | 60x |
| Run script | 0.03s | 0.8s | 27x |
Web Server
Basic HTTP Server
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javascript
Bun.serve({
port: 3000,
async fetch(req) {
const url = new URL(req.url);
if (url.pathname === "/api/hello") {
return Response.json({ message: "Hello from Bun!" });
}
return new Response("Not Found", { status: 404 });
},
});
File Serving
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javascript
Bun.serve({
port: 3000,
async fetch(req) {
const url = new URL(req.url);
const file = Bun.file(.);
return new Response(file);
},
});
WebSocket Support
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javascript
Bun.serve({
port: 3000,
fetch(req, server) {
const success = server.upgrade(req);
if (success) return undefined;
return new Response("Upgrade failed", { status: 500 });
},
websocket: {
message(ws, message) {
ws.send(message);
},
open(ws) {
ws.send("Connected!");
},
},
});
TypeScript Support
Native TypeScript
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ypescript
// app.ts
interface User {
name: string;
email: string;
}
async function getUser(id: number): Promise<User> {
const response = await fetch(/api/users/);
return response.json();
}
console.log(await getUser(1));
Run TypeScript directly:
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bun run app.ts
No s-node or sconfig.json needed!
Testing
Built-in Test Runner
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ypescript
// math.test.ts
import { expect, test } from "bun:test";
test("addition", () => {
expect(1 + 2).toBe(3);
});
test("async", async () => {
const result = await Promise.resolve(42);
expect(result).toBe(42);
});
Run tests:
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bun test
Bundling
Simple Bundle
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// bundle.js
export const greet = (name: string) => Hello, !;
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bun build bundle.js --outdir ./dist
Bundle for Browser
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bun build app.ts --outdir ./dist --target browser
Bundle for Node
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bun build app.ts --outdir ./dist --target node
Database Support
SQLite
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import { Database } from "bun:sqlite";
const db = new Database("mydb.sqlite");
// Create table
db.query("CREATE TABLE IF NOT EXISTS users (id INTEGER PRIMARY KEY, name TEXT)").run();
// Insert
db.query("INSERT INTO users (name) VALUES (?)").run("Alice");
// Query
const users = db.query("SELECT * FROM users").all();
console.log(users);
PostgreSQL
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ypescript
import postgres from "postgres";
const sql = postgres("postgres://user:password@localhost/db");
const users = await sql\SELECT * FROM users\;
console.log(users);
File Operations
Read File
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import { readFile } from "bun:fs";
const text = await readFile("hello.txt", "utf-8");
console.log(text);
Write File
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import { writeFile } from "bun:fs";
await writeFile("hello.txt", "Hello Bun!");
Read JSON
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import { readFileSync } from "bun:fs";
const data = JSON.parse(readFileSync("data.json", "utf-8"));
Comparison
| Feature | Bun | Node.js | Deno |
|---------|-----|---------|------|
| Startup Speed | 4x faster | Baseline | 2x faster |
| Package Manager | Built-in | npm | Built-in |
| TypeScript | Native | Requires setup | Native |
| Bundler | Built-in | Webpack | Built-in |
| Test Runner | Built-in | Jest | Built-in |
Framework Support
Express Alternative
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import { Elysia } from "elysia";
const app = new Elysia()
.get("/", () => "Hello Bun!")
.post("/api/users", ({ body }) => {
return { created: body };
})
.listen(3000);
React/Next.js
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# Use Bun with Next.js
bun install next react react-dom
bun run dev
Performance Benchmarks
HTTP Server
| Runtime | Requests/sec |
|---------|-------------|
| Bun | 100,000 |
| Node.js (Express) | 25,000 |
| Deno | 80,000 |
File I/O
| Operation | Bun | Node.js |
|-----------|-----|---------|
| Read 1GB file | 0.8s | 2.5s |
| Write 1GB file | 0.9s | 3.1s |
| Copy 1GB file | 0.6s | 1.8s |
Why Bun?
Use Cases
Migration from Node.js
Easy Migration
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# Replace node with bun
# Replace npm with bun install
# Replace node_modules with bun.lockb
# That's it!
Compatibility
Learning Resources
Summary
Bun represents the future of JavaScript tooling. It's faster, simpler, and more efficient than traditional Node.js setups. If you're building JavaScript applications, Bun should definitely be on your radar.
Rating: 猸愨瓙猸愨瓙猸?
Best for: Web servers, APIs, CLI tools
Learning curve: 猸?(if you know Node.js)
Performance: 猸愨瓙猸愨瓙猸?
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