IE9: Script only works in debugger, but not when NOT debugging

Question

I have some trouble with Internet Explorer's compatibility. I'm building an online tool with massive usage of HTML5 canvas, CSS3 and JavaScript. The program works fine in all major browsers, except for Internet Explorer.

IE9 switched into compatibility mode, so I set

<meta http-equiv="x-ua-compatible" content="IE=9"/>

to force IE to process the page with IE9 standards. IE does no longer fall into compatibility mode, but the script does still not work properly. Some basic functionality as drawing or dragging objects works, but only "half".

What does a programmer do in this case: He starts the debugger. And that's where the magic happens. As soon as I start the IE9 developer tools (with IE9 browser and document mode as well), the script works properly. But how should I debug a script which works fine under debugging conditions, and has errors when not debugging.

Currently, I have no clue what to do. Maybe someone can give me a hint? Thanks a lot!

Is there console lines in the code? Are there any error messages? — epascarello
– epascarello, Commented Apr 11, 2013 at 13:18
IE tends to crash on console.log() (and other console methods) unless the debugger is open - does your code use such methods? — nnnnnn
– nnnnnn, Commented Apr 11, 2013 at 13:19
Any reason you're not using IE=edge? Any users of your application on IE10 will be forced back to IE9 which could be detrimental — Aaron Powell
– Aaron Powell, Commented Apr 11, 2013 at 13:22
@nnnnnn Only in IE8 and below as console was not standardized. IE9+ will happily consume those errors — Aaron Powell
– Aaron Powell, Commented Apr 11, 2013 at 13:23
Possible reason is asynchrous calls by timer via setInterval/setTimeout or inproper usage of asynchronous functions; in this cases code execution order may differs under debugger and in clean runtime. — Tommi
– Tommi, Commented Apr 11, 2013 at 13:26

Prisoner · Accepted Answer · 2013-04-11 13:32:07Z

9

IE9 doesn't like console calls, and without showing us any code we can only guess what the issue is. You can either remove any console.log messages or use this snippet before any code is called:

(!window.console) console = {log: function() {}};

answered Apr 11, 2013 at 13:32

Prisoner

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2 Comments

TheBrain Over a year ago

Yes. If you don't have the dev tools opened, the console is not available on the page

Michael Over a year ago

The problem is solved. There were some console.log() statements. These seem to crash IE when not debugging. The problem disappears when I remove the console.log() AND the "half-working" of the script can be perfectly explained assuming the script stops at console.log() statements.

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