Web Workers is a simple means for web content to run scripts in background threads. The worker thread can perform tasks without interfering with the user interface.
Here’s a step-by-step guide on how to use Web Workers in JavaScript:
1. First, create a new Worker object and pass it the name of your JavaScript file:
```
var worker = new Worker(‘worker.js’);
```
This will start a new thread, which downloads and begins executing the ‘worker.js’ file in the background.
1. Run your code in the background by placing it into the ‘worker.js’ file:
```
//This code will run in a different thread
self.onmessage = function(e) {
var result = e.data0 + e.data1;
self.postMessage(result);
};
```
1. Communicate with the Web Worker through message passing:
To send a message to the worker, you can call the `postMessage()` function on the Worker object:
```
worker.postMessage([3, 2]); // Send data to our worker.
```
Inside the worker, an event listener picks up the message event and processes the data:
```
self.onmessage = function(e) {
var result = e.data0 + e.data1;
self.postMessage(result);
};
```
1. Listen to the worker:
Now, the main thread can listen to the worker’s message event to receive data:
```
worker.onmessage = function(e) {
console.log(‘Message received from worker’, e.data);
};
```
1. Close the worker:
If you don’t need the worker anymore, it’s a good idea to close it.
From inside the worker, you can call `close()` function:
```
self.close();
```
From the main thread, you can call `terminate()`:
```
worker.terminate();
```
This is a very basic example of Web Workers in JavaScript. However, keep in mind that Web Workers have certain limitations. For example, they don’t have access to the DOM and they can’t access global variables or JavaScript functions.
Web Workers are useful for performing computationally intensive tasks without blocking the thread that handles user interface.
