Type coercion bug in IE8 RegExp.exec()?

I don't know if this is a know problem in IE8, but I can't really find any info on it.

// The regex can vary but has to have a non-matching group defined:
var re = /^(\s)?[\d]+$/i;
// We call it with a string...
re.exec("2");
// We call it with a number...
re.exec(2);

Firefox and Chrome (can't try it in 开发者_如何转开发Opera right now) have no problem with either calls. But on IE8 the second call fails with an "Object does not support that property or method".

Is this a known bug or something?

I saw the same issues in an Ext JS 4 application. Lots of things were failing as Ext JS appears to pass numbers in the exec() method at times. The issue turned out to be a third party library SyntaxHighlighter. Removing this reverted the default IE8 behavior and re.exec(2); worked.

I'd suggest cutting down the external JS that you include in your app until you find the culprit.

Since exec takes a string I would make sure you are passing a string. By passing a number in I would say you are trying to count on grey areas of the way browsers implement javascript.