HTML5 WebWorkers look very promising but at the moment they're not supported by IE8. I'm building a business Saas and I have to support this browser for at least another 2 years.
What would happen if I started implementing a web worker thread and ran it on IE8? Would it just run on a single thread or would it just not work at all?
Thanks.
You'll get an error, because the API for creating Web Workers simply does not exist in IE.
e.g.
var worker = new Worker('my_task.js');
Will throw an error because Worker is undefined.
If you want to do feature detection, you can check first before creating the worker:
if(window.Worker !== undefined){
var worker = new Worker('my_task.js');
}
Of course, whatever task you've delegated to the webworker won't happen on non-supported browsers, which means you'll need to run the logic on the primary (non worker) context.
Since you post message to (and listen for events/messages from) WebWorkers, if you follow the same approach to your worker task you can just run it in your primary context, and make calls to it in the same way as you would if it were a webworker. This will require some additional legwork on your end, but this way you can easily switch to WebWorkers when you detect it is supported in browser.
There is a project providing a dummy implementation of web workers for IE < 10: http://code.google.com/p/ie-web-worker/ The API is the same as, but the execution is single-threaded.
It works fine but I found one issue regarding this lib. The code of the worker is executed as soon as
var worker = new Worker('myworker.js');
is called. At this moment no
worker.onmessage = function {...}
is set and messages can't be sent from the worker to the main code. So it might be necessary to start your worker code not before a message is sent from the main code to the worker, e.g.
worker.postMessage('start');
