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Alex Spinov
Alex Spinov

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Bun Has a Free JavaScript Runtime That Makes Node.js Feel Slow

#bunjs #webdev #javascript #performance

Why Bun Is Changing the JavaScript Game

If you have been building JavaScript applications with Node.js for years, you probably accepted certain truths: startup times are slow, installing packages takes forever, and you need separate tools for bundling, testing, and transpiling.

Bun throws all of that out the window. Built from scratch using Zig and JavaScriptCore (the engine behind Safari), Bun is a complete JavaScript runtime that serves as a drop-in replacement for Node.js — and it is completely free.

A friend of mine switched a production API from Node.js to Bun and saw cold start times drop by 4x. No code changes. Just swapped the runtime.

What You Get for Free

Bun is not just a runtime. It is an all-in-one toolkit:

  • JavaScript/TypeScript runtime — runs .js, .ts, .jsx, .tsx files natively
  • Package manager — bun install is up to 25x faster than npm install
  • Bundler — built-in bundler that replaces webpack/esbuild
  • Test runner — Jest-compatible testing built right in
  • Node.js compatibility — most npm packages work without changes

Getting Started in 30 Seconds 

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

# Create a new project
mkdir my-bun-app && cd my-bun-app
bun init

# Install dependencies (watch how fast this is)
bun install express
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Build a Lightning-Fast HTTP Server

Bun has a built-in HTTP server that handles 100K+ requests per second:

// server.ts — no dependencies needed
const server = Bun.serve({
  port: 3000,
  fetch(req) {
    const url = new URL(req.url);

    if (url.pathname === "/api/hello") {
      return Response.json({ 
        message: "Hello from Bun!",
        timestamp: Date.now() 
      });
    }

    if (url.pathname === "/api/data") {
      // Read a file — Bun.file() is incredibly fast
      const file = Bun.file("./data.json");
      return new Response(file);
    }

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

console.log(`Server running at http://localhost:${server.port}`);
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Run it with:

bun run server.ts
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No ts-node. No tsx. No compilation step. Bun runs TypeScript natively.

Package Manager Speed Comparison

Here is a real benchmark installing a fresh Next.js project:

# npm — 45.2 seconds
time npm install

# yarn — 32.1 seconds  
time yarn install

# pnpm — 18.7 seconds
time pnpm install

# bun — 1.8 seconds
time bun install
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Yes, you read that right. 1.8 seconds. Bun uses a global module cache and hardlinks instead of copying files.

Built-in Testing (Jest-Compatible) 

// math.test.ts
import { expect, test, describe } from "bun:test";

function fibonacci(n: number): number {
  if (n <= 1) return n;
  return fibonacci(n - 1) + fibonacci(n - 2);
}

describe("fibonacci", () => {
  test("base cases", () => {
    expect(fibonacci(0)).toBe(0);
    expect(fibonacci(1)).toBe(1);
  });

  test("computes correctly", () => {
    expect(fibonacci(10)).toBe(55);
    expect(fibonacci(20)).toBe(6765);
  });
});
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Run tests:

bun test
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SQLite Built Right In

Bun ships with a native SQLite driver — no packages needed:

import { Database } from "bun:sqlite";

const db = new Database("app.db");

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

const insert = db.prepare(
  "INSERT INTO users (name, email) VALUES (?, ?)"
);

insert.run("Alice", "alice@example.com");
insert.run("Bob", "bob@example.com");

const users = db.query("SELECT * FROM users").all();
console.log(users);
// [{ id: 1, name: "Alice", ... }, { id: 2, name: "Bob", ... }]
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When to Use Bun

Use Case Bun Ready?
REST APIs Yes
CLI tools Yes
Web scrapers Yes
Next.js apps Mostly
Production servers Yes (v1.0+)
AWS Lambda Yes

The Bottom Line

Bun is not a toy. It is a production-ready JavaScript runtime that is faster, simpler, and more complete than Node.js for most use cases. The fact that it is completely free and open-source makes it a no-brainer for new projects.

Start here: bun.sh

💡 Need web scraping or data extraction? Check out my Apify actors or email me at spinov001@gmail.com for custom solutions!

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