native-extensions.js

Element.implement({
    closest: function(selector){
        /* Matches the nearest element with the passed selector -- much like
         * Element.getParent, but with the starting element included */
        return (this.match(selector)) ? this : this.getParent(selector);
    },
    addLiveEvent: function(eventType, selector, handler){
        /* Binds a 'live event' to all the element. Whenever the event is allowed to bubble
         * up to this element, event.target is checked to see whether it matches the passed
         * selector. If it does, the handler will be fired */
        this.addEvent(eventType, (function(event){
            var target = event.target;
            var matched = target.closest(selector);
            if (matched) handler.run([event], matched);
        }).bindWithEvent(this, selector, handler));
    }
});