Technology Tales

Adventures & experiences in contemporary technology

IE6 and JavaScript performance

22nd June 2007

Having been exposed to an application at work that uses a lot of JavaScript, I fully appreciate what some mean when they talk about IE6’s inefficient handling of JavaScript. After seeing a web page taking an age to reload and your CPU taking a hammering because of JavaScript processing, the penny does tend to drop… Needless to say, this very much impacts the world of AJAX-driven web applications with their heavy dependence of client-side JavaScript. While IE7 does come to the rescue, there remain plenty of IE6 users still out there and this is reflect in website statistics. This reflects a certain level of inertia in the browser market that not only afflicts the uptake of IE7 but also the likes of Mozilla, Opera and Safari. It also means that anyone developing AJAX applications very much needs to continue testing in IE6, especially if the product of their labours is for wider public use. An example of such an application is Zimbra, an open source web application for messaging and collaboration, and the people behind it have generously share the results of their browser performance benchmarking. They did comparisons of IE6 vs. IE7 and Firefox 2 vs. IE7. IE6 easily came out as the worst in these while Firefox 2 was the best. I suppose that the next question to be asked centres around the type of code that is processed inefficiently by IE6. I wouldn’t be at all surprised if a list emerged but here’s one: using Microsoft’s proprietary innerHTML object to update the DOM for a web page format. Having a quick trawl on Google, this came up for mention as a cause of memory leaks. It is also a Microsoft innovation that never got taken up by those overseeing web standards, hardly a surprise since a spot of DOM scripting achieves the same end. It may be faster to code than any alternatives, and it does have some support from other browsers, but it does seem to have got a bad name and so should be avoided if possible. That said, it would be interesting to see a performance comparsion between innerHTML and DOM methods in IE6.

  • All the views that you find expressed on here in postings and articles are mine alone and not those of any organisation with which I have any association, through work or otherwise. As regards editorial policy, whatever appears here is entirely of my own choice and not that of any other person or organisation.

  • Please note that everything you find here is copyrighted material. The content may be available to read without charge and without advertising but it is not to be reproduced without attribution. As it happens, a number of the images are sourced from stock libraries like iStockPhoto so they certainly are not for abstraction.

  • With regards to any comments left on the site, I expect them to be civil in tone of voice and reserve the right to reject any that are either inappropriate or irrelevant. Comment review is subject to automated processing as well as manual inspection but whatever is said is the sole responsibility of the individual contributor.