So I have been trying to figure out a really simple, easy way to test the load times of my Javascript in the page, and have ended up creating a simple load time tester using jQuery called jQTester.
jQTester Displaying its results
This assumes you are using jQuery, and are running using version 1.3.1 – however it should work on most versions as the jQuery I am using is pretty lightweight.
The concept is simple – you have 2 files called start.js and end.js. Place start.js at the top, just after your <HEAD> tag, and place end.js just before </body>. Using javascript timers I am capturing the length of time between start.js loading, and the document.ready jQuery function running (when, all javascript and DOM elements should be loaded and ready to use).
Why place end.js before </body> ?
So, ideally you are placing your javascript calls at the end of the HTML document. Why? because javascript file downloads block parallel downloads in the browser. Browsers can only download 2 files per hostname at any one time, so by placing them in the <HEAD> you are in theory stopping anything else from loading within the page whilst all your javascript is being loaded. By placing them at the end of the HTML document, images etc have the chance to load first, so the perception for the user is faster load times.
So the browser will load your HTML document top to bottom. Based on the assumption that no other javascript needs to load after </body> is called, the best place to stop the timer is at that last point. That’s when the clock stops, and we assume we’re all loaded.
jQTester 0.1
So I’m not really 100% sure if this is the right way to go about this, but anyway – I’ve packaged this up as “jQTester” and am attaching version 0.1 for your perusal. It would be good to get some feedback on how I can move forward with this, as I am keen to develop a tool or plugin that can sit within the page code, rather than being a browser add-on etc.
Download jQTester 0.1
Install instructions: Use jQuery, place start.js after the <head> tag and place end.js before the </body> tag.
Add your comments below on ways to improve jQTester.
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Tags: Javascript, jQuery, Load, Tester, Timer
Very useful! I’ll probably be using this a lot. The only problem I see is there isn’t a way to close it. The only way I have to test the speed from one page to the next it to type in the URL of the next page I want to test.
Hi Steve.
Although why not something like…
var teststart=(new Date()).getTime();
…
…
…
console.log((new Date()).getTime()-teststart)
… ?
Snap. Your editor removed my html markup, but you get the gist.
There are many better ways of doing this. You can load your site even more faster by loading JavaScript files and references after content
http://www.tutkiun.com/2010/07/load-javascript-after-pageload.html