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Tuesday, February 28, 2017

jQuery - Plugins

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 https://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 jQuery Example</title>
  
      <script type = "text/javascript" 
         src = "https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.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).prop("tagName") + '".');
   });
};
Here is the example showing usage of warning() method. Assuming we put jquery.debug.js file in same directory of html page.
<html>

   <head>
      <title>The jQuery Example</title>
  
      <script type = "text/javascript" 
         src = "https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
  
      <script src = "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 alert you with following result −
This is paragraph
This is division
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