Simple Challenge: Find all the LI elements underneath two different elements (using their #ID as reference) and bind a click handler which changes the color of the LI’s text. Here is how you would do that in all of the popular event/selector libraries.

Behaviour + Prototype

Behaviour.register({
  '#item li': function(element) {
    Event.observe(element, 'click', function(event) {
      Event.element(element).setStyle({color: '#c00'});
    });
  },

  '#otheritem li': function(element) {
    Event.observe(element, 'click', function(event) {
      Event.element(element).setStyle({color: '#c00'});
    });
  }
});

Prototype 1.5.0

$$('#item li, #otheritem li').each(function(li){
  Event.observe(li, 'click', function(event) {
    Event.element(li).setStyle({color: '#c00'});
  });
});

event:Selectors

EventSelectors.start({
  '#item li:click, #otheritem li:click': function(e){
    e.setStyle('color': '#c00');
  }
});

jQuery

$("#item li, #otheritem li").click(function(){
  this.css('color', '#c00');
});

I like to think that the code speaks for itself, as to which one is the easiest to use and understand. I find it interesting how Prototype is migrating closer to what jQuery has now – while jQuery itself is blasting away with some very cool new stuff. Definitely keep your eyes peeled for new releases, as they’ll be coming soon.