Web Workers is a multi-threaded mechanism provided by the browser to place time-consuming tasks on the background thread to execute, avoiding blocking the main thread. 1. Worker does not have DOM operation permissions, and can only pass messages through postMessage and onmessage; 2. Creating a Worker requires a separate JS file and instantiated through new Worker(); 3. Common uses include data processing, image audio processing, JSON parsing, game AI computing, etc.; 4. Pay attention to cross-domain restrictions, resource consumption control and compatibility issues when using it. The rational use of Web Workers can significantly improve web page performance and user experience.
Using HTML5 Web Workers to do background tasks is actually a "threading" method to prevent the main thread from being stuck. If you run some complex calculation, data processing or timing tasks on the web page and do it directly on the main thread, the page will be stuck or even fake. Web Workers come in handy at this time.
What are Web Workers?
Simply put, Web Workers is a multi-threaded mechanism provided by the browser. It allows you to put some time-consuming tasks into a separate thread so that you don't block the user interface. For example, if you are working on an image processing application, or you need to parse a large amount of data in real time, you can throw it to Worker to do it.
It should be noted that Worker does not have DOM operation permissions and cannot access window or document objects. It is more like a "backend service" that can only receive messages, process tasks, and return results.
How to create and use Web Worker?
To use Web Worker, you must first write a separate JavaScript file, which is the execution logic of Worker. For example:
// worker.js
onmessage = function(e) {
let data = e.data;
// Do something complicated let result = data * 2;
postMessage(result);
} Then create a Worker instance in the main page and communicate via postMessage and onmessage :
const worker = new Worker('worker.js');
worker.onmessage = function(e) {
console.log('Result received:', e.data);
}
worker.postMessage(20); // Send data to WorkerThis completes a simple asynchronous communication. You can pass high-performance data structures such as arrays, objects, and even ArrayBuffer.
Frequently Asked Questions and Notes
- Cross-domain restrictions : Worker scripts must be of the same origin as the current page, otherwise an error will be reported.
- Cannot operate DOM : As mentioned earlier, Worker cannot directly update page content.
- Resource consumption control : Although Worker is an independent thread, it is not infinitely opened. Too many Workers may slow down performance.
- Compatibility is OK : mainstream modern browsers support basic Worker functionality, but not at all on older IE.
If you are using frameworks such as Vue, React, etc., you can also package Worker in combination with Webpack or Vite, and there is no need to put a separate JS file.
Suitable for Web Worker
- Encrypt or decrypt data
- Image or audio processing
- A large number of JSON parsing or generating
- AI computing in the game
- Background polling or timer tasks
If these tasks are placed in the main thread, it is easy to cause page stuttering. After sharing the burden with Worker, the user experience will be much better.
Basically that's it. Web Workers are not complicated, but are easily overlooked. Especially when doing some high-performance web applications, using Worker rationally can significantly improve response speed and overall fluency.
The above is the detailed content of Performing Background Tasks with HTML5 Web Workers. For more information, please follow other related articles on the PHP Chinese website!
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