When executing scripts in an HTML page, the page may become unresponsive until the script finishes. A web worker runs JavaScript in the background, independently of other scripts, keeping the page responsive while it operates. You can continue interacting with the page, such as clicking or selecting items, while the web worker runs.
The numbers in the table indicate the earliest browser version that fully supports Web Workers.
Before creating a web worker, verify if the user’s browser supports it:
| if (typeof(Worker) !== “undefined”) { // Yes! Web worker support! // Some code….. } else { // Sorry! No Web Worker support.. } |
Now, let’s create our web worker in an external JavaScript file. The script, stored in “demo_workers.js”, performs counting operations.
| var i = 0; function timedCount() { i = i + 1; postMessage(i); setTimeout(“timedCount()”,500); } timedCount(); |