gistfile1.js

var List = new Class({
   
    Roles: {
        'list-item': function(element) {
            element.addClass('ui-list-item');
        }
    },
   
    
    initialize: function(element) {
        
        element.getElements('[data-role]').each(function(el) {
           
           var role = el.get('data-role');
            if (this.Roles[role]) {
                this.Roles[role].apply(this, [el]);
            }
        });
    }
    
});


var element = new Element('ul').adopt([
    new Element('li[data-role=list-item]', {'text': 'Item 1'}),
    new Element('li[data-role=list-item]', {'text': 'Item 2'}),
    new Element('li[data-role=list-item]', {'text': 'Item 3'})    
  ]);

var myList = new List(element);