javascript

The Internet Explorer Event Object
Chapter 12: Events
Unlike the DOM event object, the IE event object is accessible in different ways based on the way in
which the event handler was assigned. When an event handler is assigned using the DOM Level 0
approach, the event object exists only as a property of the window object. Here is an example:
var btn = document.getElementById(“myBtn”);
btn.onclick = function(){
var event = window.event;
alert(event.type); //”click”
};
Here, the event object is retrieved from window.event and then used to determine the type of event
that was fired (the type property for IE is identical to that of the DOM version). However, if the event
handler is assigned using attachEvent(), the event object is passed in as the sole argument to the
function as shown here:
var btn = document.getElementById(“myBtn”);
btn.attachEvent(“onclick”, function(event){
alert(event.type); //”click”
});
When using attachEvent() , the event object is also available on the window object, as with the DOM
Level 0 approach. It is also passed in as an argument for convenience.
If the event handler is assigned by an HTML attribute, the event object is available as a variable called
event (the same as the DOM model). Here’s an example:
< input type=”button” value=”Click Me” onclick=”alert(event.type)” / >
The IE event object also contains properties and methods related to the specific event that caused its
creation. Many of these either map directly to or are related to DOM properties or methods. Like the
DOM event object, the available properties and methods differ based on the type of event that was
fired, but all events use the properties and methods defined in the following table.
Property/Method Type Read/Write Description
cancelBubble Boolean Read/Write False by default, but can be set to true to cancel
event bubbling (same as the DOM
stopPropagation() method)
returnValue Boolean Read/Write True by default, but can be set to false to cancel the
default behavior of the event (same as the DOM
preventDefault() method)
srcElement Element Read only The target of the event (same the DOM target
property)
type String Read only The type of event that was fired
379