Question

I use jQuery.

I have been reading a lot about selector performance and optimizing our AJAX app. I am looking to improve my selector performance. I know all the jquery performance tips. I haven’t found an exact answer to a question I have. I am using almost every current jquery performance tip and yet my app still seems to lag quite a bit.

So, to optimize I am starting with selectors.

My question is: Is descending from a context to target an id faster than just targeting the id? I can’t tell much of a difference.

Example:

Is

$('#childId', $higherElm);

faster than just

$('#childId');

????

Thanks in advance.

Answer 1

As seen in the jQuery source, $('#id') does simply document.getElementById, while $('#id', context) does $(context).find('#id'). So the first is faster.