jQuery in no-conflict mode
WordPress loads jQuery in «no conflict» mode by default. It was made for compatibility with other libraries that can be loaded as well.
In «no-confict» mode $ shortcut is not available. For example, this code will not work:
$(document).ready( function(){ $('#element') ... });
You should tweak it a bit:
jQuery(document).ready( function($){ $('#element') ... });
Pay attention to the $
sign which is passed to the function - doing so we can use $
sign in the js code.
If you don't want to wait for "DOM ready" action, you can invoke function expression immediately:
(function($) { // Here $ refers to jQuery. So you can use $. })(jQuery);