Thursday, 15 December 2011

jQuery Callback Functions


  • A callback function is executed after the current animation is 100% finished.
  • JavaScript statements are executed line by line. However, with animations, the next line of code can be run even though the animation is not finished. This can create errors.
  • To prevent this, you can create a callback function.
  • A callback function is executed after the current animation (effect) is finished.

jQuery Callback Example

The callback parameter is a function to be executed after the hide effect is completed:
  • $(selector).hide(speed,callback)

Syntax:

$("p").hide(1000,function(){
  alert("The paragraph is now hidden");
});

  Example:
 
<html>
<head>
<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript">
$(document).ready(function(){
  $("button").click(function(){
    $("p").hide(1000,function(){
      alert("The paragraph is now hidden");
    });
  });
});
</script>
</head>
<body>
<button>Hide</button>
<p>This is a paragraph with little content.</p>
</body>
</html>

Example without Callback:

Without a callback parameter, the alert box is displayed before the hide effect is completed:
 
  syntax:
 
 $("p").hide(1000);
alert("The paragraph is now hidden");
 
   Example:

 


<html>
<head>
<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript">
$(document).ready(function(){
  $("button").click(function(){
    $("p").hide(1000);
    alert("The paragraph is now hidden");
  });
});
</script>
</head>
<body>
<button>Hide</button>
<p>This is a paragraph with little content.</p>
</body>
</html>


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