Is there any differences between these jQuery selectors?

What is the difference between the three samples below and which one is better (if any)?

$("#x span").hide();

$("#x").find("span").h开发者_开发技巧ide();

$("span", "#x").hide();

They will all match the same thing; the best one is based on context. I would use the first example unless I had a variable pointing to an existing set. Then I would obviously use the find() method on it.

The old $(selector, context) (your third example) isn't seen much these days, probably because it translates to $(context).find(selector) behind the scenes anyway (and its easier to read that way).

These all make the same selection, however the first performs more poorly than the last two which perform about the same, see:

http://jsperf.com/jquery-selector-perf-right-to-left/48

http://jsperf.com/jquery-selector-context-vs-find

http://jsperf.com/jquery-selector-performance/11