Does jQuery do any kind of caching of "selectors"?

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

Always cache your selections!

It is wasteful to constantly call $( selector ) over and over again with the same selector.

Or almost always... You should generally keep a cached copy of the jQuery object in a local variable, unless you expect it to have changed or you only need it once.

var element = $("#someid");  element.click( function() {    // no need to re-select #someid since we cached it   element.hide();  });