Execute async function

execute.js

/**

 asyncexec(function(times){
  	    
    for (var x=0, y;x<times;x++) {
       y = x/2;
    }
        
    release(x);
        
}, 5000000000).then(function(x) {
  	alert('Done, iterations: '+x)
})

**/



var asyncexec = function(fn, data) {

    var canceled = false, p = new Promise(function(r, f) {

       var w = new Worker(URL.createObjectURL(new Blob([
           [
               'self.onmessage=function(e){',
                    'var release = function(result) { self.postMessage(result) }',
                    'var result = ('+fn.toString()+')(e.data, e)',
                    'if(result!==undefined) release(result);',
                '}'

           ].join("\n")
       ], { type: 'application/javascript' })));

        w.onmessage = function(e) {
            if(!canceled) r(e.data || null, e);
            w = null;
        };

        w.onerror = function(e) {
            if(!canceled) f(e);
            w = null;
        };

        w.postMessage(data);
    });

    p.cancel = function() {
    	 canceled = true;
    };

    return p;
}