Home arrow JavaScript arrow Page 3 - Understanding The JavaScript Event Model (part 1)

Handling Things - JavaScript

This may be news to you, but JavaScript comes with a powerfuland flexible event model, one which provides developers with astandardized way of trapping and handling client-side events likekeystrokes and mouse clicks. This two-part article takes an in-depthlook at how this event model works, demonstrating some practical (andnot-so-practical) uses of the most common event handlers.

TABLE OF CONTENTS:
  1. Understanding The JavaScript Event Model (part 1)
  2. Popeye() And Olive()
  3. Handling Things
  4. Red Alert
  5. Mouse Hunt
  6. Forty Two
  7. Flavour Of The Month
  8. Linking Up
  9. Game Over
By: Team Melonfire, (c) Melonfire
Rating: starstarstarstarstar / 36
June 25, 2002

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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.

 
 
>>> More JavaScript Articles          >>> More By Team Melonfire, (c) Melonfire
 

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