jquery selecter tips

Increase Specificity from Left to Right

A little knowledge of jQuery’s selector engine is useful. It works from the last selector first so, in older browsers, a query such as:

$("p#intro em");

loads every em element into an array. It then works up the parents of each node and rejects those where p#intro cannot be found. The query will be particularly inefficient if you have hundreds of emtags on the page.

Depending on your document, the query can be optimized by retrieving the best-qualified selector first. It can then be used as a starting point for child selectors, e.g.

$("em", $("p#intro")); // or
$("p#intro").find("em");