Performance of jQuery selector with context

Context really helps when you have a much larger DOM that you are searching through. Searching for IDs is already very fast and context doesn't really help that much in that case. Where context can really make a difference is when you are selecting by tag name or class.

Try testing like this: http://jsbin.com/aciji4/4

you can really see the timing get better for context when you bump up number of items in the DOM like this: http://jsbin.com/aciji4/6

It would make sense that it would take longer to use a context (vs. using a selector alone) since internally, the context uses the .find() method, so in essence, all you are really doing is

$('#context').find('#holder');

I mainly see it as an easier way to identify elements in events and iterators where the context changes because

$('.holder', this)

is prettier than

$(this).find('.holder')