Selectors.Pseudo.checked = function(){  
	return (this.get('tag') == 'input' && (this.get('type').toLowerCase() == 'radio' || this.get('type').toLowerCase() == 'checkbox') && this.checked);  
};

http://davidwalsh.name/checked-pseudo-selector-mootools

How to create a custom “:checked” pseudo selector for use in MooTools. It is just a small snippet but I’ve found it incredibly useful.

Create a Custom “:checked” Pseudo Selector for MooTools 1.2

javascript

JavaScript