Worker Threads

◆Node.js◆Worker Threads◆Concurrency◆Intermediate🎯Free Tools

Introduction

Node.js is single-threaded with an event loop. Worker threads allow you to run JavaScript in parallel, which is ideal for CPU-bound tasks like image processing, data parsing, or complex calculations.

Basic Example

worker.js

JavaScript

1	const { Worker, isMainThread, parentPort, workerData } = require("worker_threads");
2
3	if (isMainThread) {
4	const worker = new Worker(__filename, {
5	workerData: { n: 40 },
6	});
7
8	worker.on("message", (result) => console.log(result));
9	worker.on("error", console.error);
10	worker.on("exit", (code) => {
11	if (code !== 0) console.error(`Worker stopped with code ${code}`);
12	});
13	} else {
14	const { n } = workerData;
15	const fib = (x) => (x < 2 ? x : fib(x - 1) + fib(x - 2));
16	parentPort.postMessage(fib(n));
17	}

Shared Memory

shared-memory.js

JavaScript

1	const { Worker } = require("worker_threads");
2
3	const buffer = new SharedArrayBuffer(4);
4	const counter = new Int32Array(buffer);
5
6	const worker = new Worker(`
7	const { parentPort, workerData } = require("worker_threads");
8	Atomics.add(workerData.counter, 0, 1);
9	parentPort.postMessage("done");
10	`, { eval: true, workerData: { counter } });
11
12	worker.on("message", () => console.log(counter[0]));

⚠

warning

SharedArrayBuffer requires special HTTP headers (Cross-Origin-Opener-Policy and Cross-Origin-Embedder-Policy) in browser environments. In Node.js, it is available by default.

When to Use

Heavy computation that would block the event loop.
Parallel data processing pipelines.
Image, video, or audio transcoding.

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