$$ in jQuery, what's this used for?

Question

if someone just write:

 $("#downloadTabs>div").each(function(el) { el.setStyle("display", "none"); el.removeClass('active'); });

I would know what is this used for. But the actually code I read is

 $$("#downloadTabs>div").each(function(el) { el.setStyle("display", "none"); el.removeClass('active'); });

There is one more $, and what's this used for ?

James Wheare · Accepted Answer · 2009-09-22 07:57:54Z

The second example is not jQuery, it's MooTools. The $$ can take a CSS selector to return a set of elements just like the $ function in jQuery: http://mootools.net/docs/core/Element/Element#dollars

prototype.js also has a very similar $$ function that's a shortcut to getElementsBySelector: http://www.prototypejs.org/api/utility/dollar-dollar

Ah yeah it's MooTools. The difference being removeClass is called removeClassName in prototype.

nickf · Accepted Answer · 2009-09-22 07:44:33Z

It might well be that to avoid conflicts with some other library, someone working on your codebase has added a line like this:

var $$ = $.noConflict();

$$ is not mentioned in the jQuery source code as far as I can see...

Jan Jongboom · Accepted Answer · 2009-09-22 07:53:17Z

Yet jquery could have $$, as stated in this article:

3 Answers 3