Editing JavaScript/Notes/IBD

== Interface Based Design ==
Registering event handlers. 

=== Two ways to Register Events ===
An event is a notification that something has occurred. 

==== Event Name as a Property ====
"DOM 0" Events. Each event is a property name. The value is one function, or null. 

<source lang="javascript">
el["onclick"] = function(ev) {
  alert(this);
};
</source>
Custom objects
<source lang="javascript">
userPicker.onuserselected= function(ev) {
  console.log(ev.user + " chosen.");
};
</source>

==== Event Listener Interface ====
<source lang="javascript">
el.addEventListener("click", function(ev) {
  alert("clicked");
}, false);
</source>

Custom objects
<source lang="javascript">
userPicker.addCallback("onuserselected", function(ev) {
  console.log(ev.user + " chosen.");
});
</source>