JQuery

From XPUB & Lens-Based wiki

JQuery is a JavaScript popular framework. It smooths over many of the difficulties that traditionally made JavaScript hard to work with and supports / encourages a unique style of coding driven by CSS-selector based "queries". JQuery code can be surprisingly compact.

For example, to hide all the links (in anchor tags) on a page, you could simply write:

$("a").hide();

http://jquery.org