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