$.unique goes into an infinite loop in IE8 (slow script warning).

[dangerbell]

​http://jsfiddle.net/QAWyd/2/

The above jsFiddle will trigger a slow script warning in IE8 (but not Chrome, I haven't checked other IEs).

It seems to be the condition in the for loop of Sizzle.uniqueSort.

for ( ; (elem = results[i]); i++ ) {
  if ( elem === results[ i - 1 ] ) {
    results.splice( i--, 1 );
  }
}

In Chrome when results[i] accesses an element that's been removed with splice it returns undefined. But in IE8 it seems that it can still access the element and assigns it to elem. So the condition always ends up being true. Array indexes that are outside the original array's length return undefined and results.length returns the correct size. I have no idea why IE would do this.

The loop from jQuery 1.7.2 works properly because it's checking results.length.

[dmethvin]

The documentation says:

This function only works on plain JavaScript arrays of DOM elements, and is chiefly used internally by jQuery. -- ​http://api.jquery.com/jQuery.unique/

You're passing it a jQuery object. Did you notice the documentation?

[dangerbell]

Replying to dmethvin:

The documentation says:

This function only works on plain JavaScript arrays of DOM elements, and is chiefly used internally by jQuery. -- ​http://api.jquery.com/jQuery.unique/

You're passing it a jQuery object. Did you notice the documentation?

Oh. Yep, it works if you pass it a regular array. I guess I'll go report this as a bug in the plugin I was using. Thanks.

[dmethvin]

Great! Which plugin was this?

[dangerbell]

Replying to dmethvin:

Great! Which plugin was this?

jqBootstrapValidation: ​http://reactiveraven.github.com/jqBootstrapValidation/

[dmethvin]

I'll file a bug on their issue tracker, thanks!