jQuery Selectors, efficiency

Question

I have been reading more lately about the efficiency of the different selector engines. I know that jQuery uses the Sizzle engine and this blog post about some jQuery stuff

Answer 1

You can see from the source code here: http://code.jquery.com/jquery-1.6.2.js in the function init.

The fastest selector is $('') which just returns an empty jQuery object immediately.

$('body') is next, which jQuery converts to document.body

The next is $('#id') which uses document.getElementById('id').

Any other selector such as $('div#id') will just become a call to $(document).find('div#id'). find() is very complex compared to any of those other solutions and uses Sizzle JS to select the div.