Question

I have had this feeling that $('.class:first') runs faster than $('.class'). So anytime I know there only is one .class in the subset, I’ve used it.

Does :first make the query run faster, or is it unnecessary?

Answer 1

It actually depends on the browser, :first isn’t a CSS selector, it’s a jQuery filter – so that requires some extra parsing work…where as .class by itself can be handed off to a native browser selector method (e.g. document.querySelectorAll() here).

Any of these would actually be faster:

$('.class').first()
//or...
$('.class').eq(0)
//or fastest:
$('.class').slice(0, 1)

…since they run native code then just take the first entry in that set.