

Essential performance best practices for jQuery - samgro
http://www.artzstudio.com/2009/04/jquery-performance-rules/

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alexh
I was under the impression that jQuery cached selectors, so the advice "Cache
jQuery Objects", while smart for many reasons, would not actually affect
performance much at all.

Was I wrong?

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dmethvin
It depends on the selector and the browser. Something like $(".myclass") is
worth caching on IE7 because it requires a pass through the entire document;
there's no `querySelectorAll` or `getElementsByClassName`.

I wouldn't start by caching selectors all over the place unless you profile
and see that it's slow. Doing a lot of selecting in a `scroll` or `mousemove`
handler would be a bad idea though: <http://ejohn.org/blog/learning-from-
twitter/>

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whichdan
So is it generally agreed that $(window).load() should be used over
$(document).ready() in most cases?

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dmethvin
I think the point there was that if you have a lot of setup to do, try to
defer as much as possible past `.ready()` so that the user will have something
to look at.

However, if you wait until the `load` event happens, the page is visible and
the user can start interacting with it. If you're still messing with the HTML
at that point it can be pretty confusing for the user. That's really common
with pages that decide for example to AJAX back for saved settings; they can
yank the defaults out from under you while you're typing! The southwest.com
site does that and it drives me crazy.

None of the recommendations should be seen as absolutes, and some conflict
with each other. For example, if you're using event delegation you've got to
be careful in caching selectors to content that may go away.

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samgro
Oldie but goodie. Point #7, "Leverage Event Delegation", was particularly
helpful for me.

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rimantas
Just don't forget that you can use .delegate() now, instead of the solution
offered in the article (which is more than two years old).

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jasonwatkinspdx
A lot of this is outdated.

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DanielRibeiro
Yeah, the article is from April 2009. I realized that when he mentioned jQuery
1.3.

