IE Performance Issues Adding Dom Nodes

October 12, 2009

My app has a search screen that fetches the results via Ajax and displays them in a table. Worked fine in Firefox, but in IE there’s a slight processor jump for a second or so. Strange, but not a problem. The users of this app, however, use a remote desktop app to run IE to access it. And when they did the search, their CPU would hit 100% for 1-5 minutes, making the entire terminal completely unusable.

I agonized over different JavaScript fixes: removed a table JS widget, switched off of tables altogether, switched to innerHTML, used DocumentFragments. Nothing worked.

Then, on a whim, I disabled all the CSS files on the app, and it worked like a charm. As I narrowed it down, I discovered that some CSS I was using to emulate frames (non-scrolling header, footer, and sidebar) was the offending code.

Let’s step back and think about that one again. What caused the processor to hit 100% for 5 minutes was not JavaScript, but CSS.

Sigh. So, if you have an issue with IE hitting 100% processor load for any reason, don’t assume that JS is necessarily the problem. Try disabling your CSS and see if that fixes it.

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IE “Expected identifier, string or number”

October 9, 2008

After getting a script to work in Firefox, I tried it out in IE, but got the errorĀ “Expected identifier, string or number.” Turns out Firefox is OK with you putting a comma after the final element in a list, but IE is not.