jQuery-13

jQuery - Plugins

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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.

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