Web Workers 是瀏覽器提供的 JavaScript 多線程解決方案，允許在主線程之外運行腳本，解決復雜計算導致的頁面卡頓問題。本文主要講解Web Workers 的核心原理及使用場景和進階技巧。一、核心機制
1. 線程模型
2. 特性限制
二、基礎使用
1. 創建專用 Worker（Dedicated Worker）
主線程代碼：
const worker = new Worker('worker.js');
worker.postMessage({ type: 'CALC', data: [1, 2, 3] });
worker.onmessage = (e) => { console.log('Result:', e.data);};
worker.onerror = (err) => { console.error('Worker error:', err);};
self.onmessage = function(e) { if (e.data.type === 'CALC') { const sum = e.data.data.reduce((a, b) => a + b, 0); self.postMessage(sum); }};
2. 終止 Worker
worker.terminate();
self.close();
三、5 大應用場景
1. 復雜計算
worker.postMessage({ nums: Array(1e6).fill(Math.random()) });
self.onmessage = (e) => { const sum = e.data.nums.reduce((acc, num) => acc + num, 0); self.postMessage(sum);};
2. 圖像處理
canvas.addEventListener('imageUpload', (e) => { const imageData = ctx.getImageData(0, 0, canvas.width, canvas.height); worker.postMessage(imageData);});
self.onmessage = (e) => { const data = e.data.data; for (let i = 0; i < data.length; i += 4) { const avg = (data[i] + data[i+1] + data[i+2]) / 3; data[i] = data[i+1] = data[i+2] = avg; } self.postMessage(e.data);};
3. 大數據分析
self.onmessage = (e) => { const rawData = e.data; const results = rawData .filter(item => item.age > 30) .map(item => ({ ...item, score: item.value * 2 })); self.postMessage(results);};
4. 實時數據流處理
const ws = new WebSocket('wss://api.example.com/stream');
ws.onmessage = (event) => { worker.postMessage(JSON.parse(event.data));};
5. 定時任務調度
let count = 0;function preciseTimer() { count++; self.postMessage(count); setTimeout(preciseTimer, 1000);}preciseTimer();
四、進階技巧
1. 傳輸大內存數據（Transferable Objects）
避免數據拷貝，直接轉移內存所有權：
const buffer = new ArrayBuffer(1024 * 1024 * 100); worker.postMessage(buffer, [buffer]);
2. Worker 池管理
class WorkerPool { constructor(poolSize, workerScript) { this.pool = Array(poolSize).fill().map(() => new Worker(workerScript)); this.taskQueue = []; }
exec(data) { return new Promise((resolve) => { const worker = this.pool.find(w => !w.busy); if (worker) { worker.busy = true; worker.postMessage(data); worker.onmessage = (e) => { worker.busy = false; resolve(e.data); }; } else { this.taskQueue.push({ data, resolve }); } }); }}
3. SharedArrayBuffer + Atomics
共享內存 + 原子操作（需 HTTPS 環境）：
const sab = new SharedArrayBuffer(1024);const arr = new Int32Array(sab);worker.postMessage(sab);
self.onmessage = (e) => { const sharedArr = new Int32Array(e.data); Atomics.add(sharedArr, 0, 1); };
五、注意事項
1.數據序列化成本：頻繁傳遞大對象時優先使用 Transferable Objects
2.生命周期管理：及時調用 terminate() 避免內存泄漏
3.兼容性策略：
if (window.Worker) { } else { }
4.調試技巧：Chrome DevTools → Sources → Threads 可調試 Worker
學會 Web Workers 能顯著提升 Web 應用的響應速度和復雜任務處理能力，合理使用可突破單線程限制，打造更專業的瀏覽器端應用。
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該文章在 2025/3/25 10:30:33 編輯過
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