how to select event by class in prototype

Question

in jQuery. i am invoking an event by class. how do you do same in Prototype.

$(".button").click(function() {
  var element = $(this);
  var Id = element.attr("id");
});

Answer 1

$$('.button').observe('click', respondToClick);

function respondToClick(event) {
   var element = event.element();
   var Id = element.id;
}

http://www.prototypejs.org/api/event