Node.js

Node.js is a cross-platform JavaScript runtime environment. Node.js 22 (LTS 2025) brings native TypeScript support (experimental), a built-in Test Runner, and a native WebSocket client.

When to Use

• Real-time Apps: Chat, Gaming, Collaboration (WebSockets).
• API Servers: High concurrency with non-blocking I/O.
• Tooling: The foundation of modern frontend toolchains (Vite, Next.js).

Quick Start (Native Features)

// Native Test Runner (No Jest needed)
import { test, assert } from "node:test";

test("synchronous passing test", (t) => {
  assert.strictEqual(1, 1);
});

// Native WebSocket
const ws = new WebSocket("ws://example.com/socket");
ws.onopen = () => console.log("Connected");

Core Concepts

Event Loop

Single-threaded, non-blocking I/O. Heavy CPU tasks block the loop (bad), but I/O tasks are offloaded to OS (good).

Streams

Process huge files piece-by-piece without loading them into memory.

Native APIs (2025)

Node now has fetch, test, watch, and .env support built-in. You need fewer dependencies than in 2020.

Best Practices (2025)

Do:

• Use node:test: Drop Jest/Mocha for simple projects.
• Use node --env-file: Drop dotenv dependency.
• Use Async/Await: Callbacks are dead. Long live Promises.

Don't:

• Don't block the Event Loop: Don't run Crypto or Image processing on the main thread. Use Worker Threads.
• Don't use require: New projects should use ESM (import).

References

• Node.js Documentation