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Understanding The JavaScript Event Model (part 1)
The JavaScript event model hides a whole lotta surprises. Take a look.

| Handling Things |

Unlike some other programming languages, JavaScript doesn't require you to declare and define functions before they're called. So it's possible to invoke a function via an event handler, and define that function later on in your script - as the following example demonstrates:


<html>
<head>
</head>

<body>

<a href="http://somewhere" onMouseOver="popeye()" onMouseOut="olive()"><img name="myimage" src="normal.jpg"></a>

<script language="JavaScript">
function popeye()
{
document.myimage.src='hover.jpg';
}

function olive()
{
document.myimage.src='normal.jpg';
}
</script>
</body>
</html>


If modularizing your code into functions isn't really your cup of tea (why ever not?!), you can even have the JavaScript code accompany the event handler directly.


<html>
<head>
</head>

<body>

<a href="http://somewhere" onMouseOver="document.myimage.src='hover.jpg'" onMouseOut=" document.myimage.src='normal.jpg'"><img name="myimage" src="normal.jpg"></a>

</body>
</html>


JavaScript comes with handlers for most common user events...and quite a few uncommon ones. Here's a brief list of the more important ones.

onAbort - invoked when the user aborts the loading of an image by clicking the STOP button

onClick - invoked when the user clicks the specified object

onFocus - invoked when the target object receives focus

onBlur - invoked when the target object loses focus

onMouseOver - invoked when the user passes the mouse over the target object

onMouseOut - invoked when the mouse pointer leaves the target object

onSubmit - invoked when the user clicks the Submit button in a form

onChange - invoked when the user changes the contents of a text field

onSelect - invoked when the user selects the contents of a text field

onReset - invoked when the user clicks the Reset button in a form

onLoad - invoked when the target image or document is loaded

onUnload - invoked when the target image or document is unloaded

Let's now look at these in greater detail.


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