Web Workers avec les threads WASM
Intégrez des Web Workers pour exécuter des modules WASM sur des threads distincts, éviter de bloquer l’interface et améliorer sa réactivité.
Web Workers avec les threads WASM est une leçon WebAssembly (WASM) for High Performance Apps gratuite sur CoddyKit. Ceci est la leçon 1 sur 4. Tu peux lire la leçon complète ci-dessous gratuitement — puis la pratiquer en direct dans le navigateur avec un éditeur de code intégré et un tuteur IA 24/7. Elle fait partie du parcours d'apprentissage WebAssembly (WASM) for High Performance Apps, et ta progression se synchronise sur le web et l'application CoddyKit. Le cours WebAssembly (WASM) for High Performance Apps comprend 4 leçons au total.
Certaines parties de cette leçon n'ont pas encore été traduites et s'affichent en anglais.
Preventing UI Freezes
Web applications often need to perform complex tasks, like heavy calculations or data processing. If these tasks run directly on the main browser thread, they can cause the user interface (UI) to freeze and become unresponsive.
This leads to a poor user experience. To avoid this, we need ways to run code concurrently, or in parallel, without blocking the UI.
Meet Web Workers
Web Workers are a JavaScript feature that allows scripts to run in the background, separate from the main execution thread of a web page.
- They have their own global scope.
- They cannot directly access the Document Object Model (DOM).
- They communicate with the main thread using messages.
This isolation is key to keeping your UI responsive.
WASM on the Main Thread
By default, when you load and execute a WebAssembly (WASM) module in a web page, it runs on the main JavaScript thread, just like regular JavaScript code.
If your WASM module performs a very long or computationally intensive operation, it will block the main thread. This means the browser won't be able to update the UI, respond to user input, or run other scripts until the WASM task is complete.
WASM + Workers = Power
Combining Web Workers with WebAssembly offers a powerful solution for high-performance web applications. You can:
- Run CPU-intensive WASM computations (like image processing, video encoding, or complex simulations) in a separate thread.
- Keep the main thread free and responsive for UI updates and user interactions.
- Leverage the near-native speed of WASM without sacrificing user experience.
Spawning a Web Worker
You create a Web Worker by instantiating the Worker object with the URL of a script file. This script will then run in its own thread.
The main script can then send messages to this worker, and the worker can send messages back.
const workerCode = `
self.onmessage = (e) => {
console.log('Worker received:', e.data);
self.postMessage('Worker says hello!');
};
`;
const blob = new Blob([workerCode], { type: 'application/javascript' });
const worker = new Worker(URL.createObjectURL(blob));
worker.onmessage = (event) => {
console.log('Main received:', event.data);
};
worker.postMessage('Hello from main!');
console.log('Main thread finished setup.');Loading WASM in a Worker
Loading a WASM module inside a Web Worker is similar to loading it on the main thread. You fetch the .wasm file and instantiate it using WebAssembly.instantiate within the worker's script.
Once instantiated, you can call its exported functions to perform your heavy computations.
// worker.js
self.onmessage = async (e) => {
// Fetch the WASM module
const response = await fetch('my_wasm_module.wasm');
const bytes = await response.arrayBuffer();
// Instantiate the WASM module
const { instance } = await WebAssembly.instantiate(bytes, {});
// Call an exported WASM function
const result = instance.exports.processData(e.data);
// Send result back to the main thread
self.postMessage(result);
};Communicating with Workers
Communication between the main thread and a Web Worker happens via messages using the postMessage() method and the onmessage event handler.
Data passed between threads is copied, not shared, which means complex objects are serialized and deserialized. This ensures thread safety.
const workerCode = `
self.onmessage = (e) => {
console.log('Worker got:', e.data);
self.postMessage('Processing ' + e.data);
};
`;
const blob = new Blob([workerCode], { type: 'application/javascript' });
const worker = new Worker(URL.createObjectURL(blob));
worker.onmessage = (event) => {
console.log('Main got:', event.data);
};
worker.postMessage('a large dataset');
worker.postMessage('another task');
console.log('Main thread sent messages.');Offloading Heavy Calculations
This example demonstrates how to offload a simulated heavy calculation to a Web Worker. The main thread sends a number, the worker performs a Fibonacci-like calculation, and the main thread continues its work without interruption.
Imagine the worker's heavyCalculation function is actually your WASM module's high-performance function.
const workerCode = `
self.onmessage = (e) => {
console.log('Worker: Starting heavy calculation...');
const num = e.data;
let a = 0, b = 1, next;
for (let i = 0; i < num; i++) {
next = a + b;
a = b;
b = next;
}
console.log('Worker: Calculation finished.');
self.postMessage(a);
};
`;
const blob = new Blob([workerCode], { type: 'application/javascript' });
const worker = new Worker(URL.createObjectURL(blob));
worker.onmessage = (event) => {
console.log('Main: Received result:', event.data);
};
worker.postMessage(40); // Send number to worker
console.log('Main: Sent request. UI remains responsive!');
// Simulate other UI work on the main thread
let counter = 0;
const intervalId = setInterval(() => {
console.log('Main: UI update simulation ' + counter++);
if (counter > 3) clearInterval(intervalId);
}, 100);Key Advantages
Using Web Workers with WASM modules brings several significant benefits to your web applications:
- Improved UI Responsiveness: The main thread stays free, preventing freezes.
- Better Performance: Combine WASM's speed with parallel execution.
- Enhanced User Experience: Users experience fluid interactions even during intensive tasks.
- Efficient Resource Utilization: Leverage multi-core CPUs by distributing workload.
Check Your Understanding
Consider a web application that needs to perform complex image filtering. This process takes several seconds to complete.
Which approach would best ensure the user interface remains responsive?
Summary & Next Steps
We've learned how Web Workers provide a separate thread for executing scripts, preventing UI blocking. By loading and running your high-performance WASM modules inside these workers, you can achieve smooth, responsive web applications even with heavy computations.
This combination is powerful for tasks like image processing, data analysis, and complex simulations. In the next lessons, we'll explore more advanced concurrency patterns, including shared memory for even tighter integration.
Apprends WebAssembly (WASM) for High Performance Apps avec un tuteur IA — gratuit
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- Cours
- 12
- Leçons
- 48
Questions Fréquemment Posées
La leçon « Web Workers avec les threads WASM » est-elle gratuite ?
Oui — le texte complet de « Web Workers avec les threads WASM » est gratuit à lire ici sur le web. Pour la pratiquer de manière interactive (un éditeur de code intégré et un tuteur IA 24/7) et déverrouiller le reste du cours WebAssembly (WASM) for High Performance Apps, passe à CoddyKit PRO. Le cours WebAssembly (WASM) for High Performance Apps comprend 4 leçons au total.
Qu'est-ce que j'apprendrai dans « Web Workers avec les threads WASM » ?
Intégrez des Web Workers pour exécuter des modules WASM sur des threads distincts, éviter de bloquer l’interface et améliorer sa réactivité. Tu pratiques WebAssembly (WASM) for High Performance Apps avec du code pratique que tu exécutes directement dans le navigateur, et un tuteur IA 24/7 répond à tes questions au fur et à mesure que tu avances dans la leçon.
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Aucune expérience préalable n'est requise. WebAssembly (WASM) for High Performance Apps sur CoddyKit est structuré pour les débutants jusqu'aux apprenants avancés, donc tu peux commencer ici ou depuis le début et avancer à ton rythme. Ceci est la leçon 1 sur 4.
Combien de temps prend la leçon « Web Workers avec les threads WASM » ?
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Peux-tu écrire et exécuter du code dans cette leçon WebAssembly (WASM) for High Performance Apps ?
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Toutes les leçons de ce cours
- Web Workers avec les threads WASM
- SharedArrayBuffer et opérations atomiques pour WASM
- Concevoir des applications WASM concurrentes
- Communication par messages et canaux entre threads WASM