Undersgtanding the Syntax of jQuery - YUI3 - AlloyUI

Getting Started

1.  jQuery 1.4.2     : $('div.foo:first')

2.  YUI 3.3.0        : Y.one('div.foo')

3.  AUI 1.0.1        : A.one('div.foo')

jQuery, YUI3, & AUI use similar selector syntax, but jQuery has added extensions, mainly convenience pseudo-classes, to the Sizzle CSS3-compliant selector engine. YUI3 & AUI comes with three different selector engines; see the section on Selectors.

Please go through below site for more details.I found it very helpful.
            Jquery -- YUI -- AUI (Syntax diff)
Thanks
Srikanth