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Is there a performance penalty for using an overly broad selector?

in Using jQuery • 10 years ago

I just tried using a specific selector but after ~30 attempts gave up and used a broad selector.

In the wrong context the functionality of the selector won't hurt anything. But the right context is maybe 1 out of 100 of the elements selected.

Do I pay a performance penalty for this? It's something very broad like:

$(document).on("click", "li", function() { $("[blocked]").removeClass("ui-disabled"); } );

Where li is the selector I am concerned about being too broad. There are maybe 200 li's on the page.

Replies(4)

jakecigar

Re: Is there a performance penalty for using an overly broad selector?

10 years ago

$('.ui-disabled").filter('[blocked]').removeClass("ui-disabled");

would probably be more efficient.

JΛ̊KE

seanmchug..

Re: Is there a performance penalty for using an overly broad selector?

10 years ago

Sorry for not being more clear. That line was just an abstract example to give a rough idea of what I was talking about. The real question is if there is a performance penalty for using an overly broad selector when the element you are looking for is only a tiny fraction of the elements retrieved by the selector.

For example if you attach a click to li but there are 10,000 li's on the page.

I know the quick answer is to say just slap an id on it or use a better selector or whatever. But in the extremely rare case where you might just end up using li (again li is just a concept not an exact element) do you pay any significant performance penalty?

jakecigar

Re: Is there a performance penalty for using an overly broad selector?

10 years ago

It’s hella-more efficient than doing individual ons. But, less efficient than

$('ul').on("click", "li", function()

$('#aParticularUL').on("click", "li", function()

Limiting to some element in the dom, and going live-on down from it is the most efficient.

JΛ̊KE

jakecigar

Re: Re: Is there a performance penalty for using an overly broad selector?

10 years ago

Part of the beauty of this format of on, is that there is only one click attached. But is has to see if the click is actually on the li, and not on something else.

This format can be a killer!

$('li').on('click',function()… // 10,000 attached functions.

JΛ̊KE

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