Event Handler Registration

Register even handler by calling addEventListener(event, function-to-call, capturing-phase?) on desired element.
- document.myform.addEventListener("submit", function (e) {return validate(e.target);}, false);
- The event type is the lowercase name of the HTML handler attribute with the “on” removed.
- The function is the one to call. It is passed and Event object which contains more info about the event.
- The final argument is true if you want to capture events during the capturing phase of event propagation.
You can call addEventListener() multiple times on an element. No order guarantees.
Adding the same function again is ignored.
removeEventListener() takes the same arguments.