Performance of jQuery Selectors with ID

Question

I know in jQuery if we use ID to select elements,it\'s so efficient.I have a question about this selectors:

please consider this 3 selectors:

Answer 1

A couple things:

• More selectors = slower search. If you can get your desired result with fewer predicates, do so.
• Getting an element by ID is quicker than getting by a class. getElementById is a core function of JavaScript that is heavily optimised because it is used so frequently. Leverage this when possible.
• The space selector (' ') is much more costly than the child selector ('>'). If you can use the child selector, do so.

These rules apply to CSS as they do JavaScript and jQuery.