A plug-in is piece of code written in a standard JavaScript file. These files provide useful jQuery methods which can be used along with jQuery library methods.
There are plenty of jQuery plug-in available which you can download from repository link at http://jquery.com/plugins.
How to use Plugins:
To make a plug-in’s methods available to us, we include plug-in file very similar to jQuery library file in the <head> of the document.
We must ensure that it appears after the main jQuery source file, and before our custom JavaScript code.
Following example shows how to include jquery.plug-in.js plugin:
<html>
<head>
<title>the title</title>
<script type="text/javascript"
src="/jquery/jquery-1.3.2.min.js"></script>
<script src="jquery.plug-in.js" type="text/javascript">
</script>
<script src="custom.js" type="text/javascript"></script>
<script type="text/javascript" language="javascript">
$(document).ready(function() {
.......your custom code.....
});
</script>
</head>
<body>
.............................
</body>
</html> |
How to develop a Plug-in
This is very simple to write your own plug-in. Following is the syntax to create a a method:
jQuery.fn.methodName = methodDefinition; |
Here methodNameM is the name of new method and methodDefinition is actual method definition.
The guideline recommended by the jQuery team is as follows:
- Any methods or functions you attach must have a semicolon (;) at the end.
- Your method must return the jQuery object, unless explicity noted otherwise.
- You should use this.each to iterate over the current set of matched elements – it produces clean and compatible code that way.
- Prefix the filename with jquery, follow that with the name of the plugin and conclude with .js.
- Always attach the plugin to jQuery directly instead of $, so users can use a custom alias via noConflict() method.
For example, if we write a plugin that we want to name debug, our JavaScript filename for this plugin is:
jquery.debug.js |
The use of the jquery. prefix eliminates any possible name collisions with files intended for use with other libraries.
Example:
Following is a small plug-in to have warning method for debugging purpose. Keep this code in jquery.debug.js file:
jQuery.fn.warning = function() {
return this.each(function() {
alert('Tag Name:"' + $(this).attr("tagName") + '".');
});
}; |
Here is the example showing usage of warning() method. Assuming we put jquery.debug.js file in /jquery subdirectory:
<html>
<head>
<title>the title</title>
<script type="text/javascript"
src="/jquery/jquery-1.3.2.min.js"></script>
<script src="/jquery/jquery.debug.js" type="text/javascript">
</script>
<script type="text/javascript" language="javascript">
$(document).ready(function() {
$("div").warning();
$("p").warning();
});
</script>
</head>
<body>
<p>This is paragraph</p>
<div>This is division</div>
</body>
</html> |
This would produce following result:
Tag Name:"DIV" Tag Name:"P" |
To understand it in better way you can Try it yourself.