measure processing time of AJAX call

I want to mea开发者_StackOverflow社区sure how long it takes to process AJAX call. I have it up and running but don't know how to code this in javascript (js only)

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var start = new Date().getTime();
doAjax({
  success: function() {
    var end = new Date().getTime();
    console.log('milliseconds passed', end - start);
  }
});

save a time value before you start doing ajax stuff, and then do it again when it finishes. Then subtract one form the other and get your time.

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This will not give accurate timings because javascript uses an event queue. That means your program may execute like this:

• Start AJAX request
• Handle a waiting mouse click event / any other waiting line of code in the meantime
• Start handling the AJAX ready response

Unfortunately there is no way to get the time the event was added to the queue as far as I know. Event.timeStamp returns the time the event was popped from the queue, see this fiddle: http://jsfiddle.net/mSg55/.

Html:

<a href="#">link</a>
<div></div>

Javascript:

$(function() {
    var startTime = new Date();
    $('a').click(function(e) {
        var endTime = new Date(e.timeStamp);
        $('div').append((endTime - startTime) + " ");
        //produce some heavy load to block other waiting events
        var q = Math.PI;
        for(var j=0; j<1000000; j++)
        {
            q *= Math.acos(j);
        }
    });

    //fire some events 'simultaneously'
    for(var i=0; i<10; i++) {
        $('a').click();
    }
});