Javascript code for making my browser slow down

Question

I\'m writing a library for WebWorkers, and I want to test the difference between running a script in the main page thread, versus in one or more workers. The problem is: I can\'

Answer 1

Maybe this is what you are looking for:

    var threadTest = function(durationMs, outputFkt, outputInterval) {
        var startDateTime = (new Date()).getTime();
            counter = 0,
            testDateTime = null,
            since = 0, 
            lastSince = -1;

        do {
            testDateTime = (new Date()).getTime();
            counter++;

            since = testDateTime - startDateTime;

            if(typeof outputFkt != 'undefined' && lastSince != since && testDateTime % outputInterval == 0) {
                outputFkt(counter, since);
                lastSince = since;
            }
        } while(durationMs > since);

        if(typeof outputFkt != 'undefined') {
                outputFkt(counter, since);
        }

        return counter;
    }

This method will simply repeat a check in a loop

durationMS - duartion it should run in miliseconds

OPTIONAL:
outputFkt - a callback method, for logging purpose function(currentCount, milisecondsSinceStart)
outputInterval - intervall the output function will be called

I figured since you do not want to test a real function, and even NP-Hard Problems have a ratio between input length and time this could be a easy way. You can measure performance at any interval and of course receive the number of loops as a return value, so you can easily measure how much threads interfere each others performance, with the callback even on a per cycle basis.

As an example here is how i called it (jQuery and Dom usage are here, but as you can see optional)

$(document).ready(function() {
    var outputFkt = function(counter, since) {
        $('body').append('
'+counter+', since '+since+'
');    
    };

    threadTest(1000, outputFkt, 20);

});

A last Warning: Of course this function can not be more exact than JS itself. Since modern Browsers can do much more than one cycle in one Milisecond, there will be a little tail that gets cut.

Update

Thinking about it... actually using the ouputFkt callback for more than just output could give great insight. You could pass a method that uses some shared properties, or you could use it to test great memory usage.