Is it possible to terminate a running web worker?

Question

I have a web worker running a time-consuming routine task with ajax-requests. Can I terminate them from a main thread not waiting for them to finish?

That's how I spawn and terminate it:

$("button.parse-categories").click(function() {
    if (parseCategoriesActive==false) {
        parseCategoriesActive = true;
        parseCategoriesWorker = new Worker("parseCategories.js");


        $("button.parse-categories-cancel").click(function() {
            parseCategoriesWorker.terminate();
            parseCategoriesActive = false;
        });             
    }
});

This is the worker code:

function myAjax(url, async, callback) {
    xmlhttp = new XMLHttpRequest();
    xmlhttp.onreadystatechange=function() {
        if (xmlhttp.readyState==4 && xmlhttp.status==200)
            callback(xmlhttp.responseText);
        if (xmlhttp.readyState==4 && xmlhttp.status!=200) {
            self.postMessage("error");
            throw "error in ajax: "+xmlhttp.status;
        }
    }
    xmlhttp.open("GET", url, async);
    xmlhttp.send();
}

var parseCategoriesActive = true;
var counter = 0;
do {
    myAjax('parser.php', false, function(resp) {
        if (resp=='success')
            parseCategoriesActive = false;
        else {
            counter += Number(resp);
            self.postMessage(counter);
        }       
    });
} while (parseCategoriesActive==true);

Answer 1

You can kill any webworker using terminate().

Citing from MDN:

The Worker.terminate() method immediately terminates the Worker. This does not offer the worker an opportunity to finish its operations; it is simply stopped at once.