Question

For example, will the first piece of code perform a full search twice, or is it smart enough to cache results if no DOM changes have occurred?

if ($('#navbar .heading').text() > '') {   $('#navbar .heading').hide(); } 

and

var $heading = $('#navbar .heading');  if ($heading.text() > '') {   $heading.hide(); } 

If the selector is more complex I can imagine it’s a non-trivial hit.

Answer 1

jQuery doesn’t, but there’s the possibility of assigning to variables within your expression and then use re-using those in subsequent expressions. So, cache-ifying your example …

if ((cached = $('#navbar .heading')).text() > '') {   cached.hide(); } 

Downside is it makes the code a bit fuglier and difficult to grok.