stripe.js

var subs = YAHOO.util.Dom.getElementsByClassName('sub', 'ul');
for(var i = 0; i < subs.length; i++){
    var subListChildren = YAHOO.util.Dom.getChildren(subs[i]);
    for(var k = 1; k < subListChildren.length + 1; k=k+2){
        YAHOO.util.Dom.addClass(subListChildren[k], 'even');
    }
}

var li_els = YAHOO.util.Selector.query("ul.sub li:nth-child(2n)").forEach( function(li) { DOM.addClass(li,"even") } );