Using JQuery in Drupal 7

From the Drupal 7 upgrade guide:

Javascript should be made compatible with other libraries than jQuery by adding a small wrapper around your existing code:

(function ($) {
  // Original JavaScript code.
})(jQuery);

The $ global will no longer refer to the jquery object. However, with this construction, the local variable $ will refer to jquery, allowing your code to access jQuery through $ anyway, while the code will not conflict with other libraries that use the $ global.

You can also just use the 'jQuery' variable instead of the $ variable in your code.

According to Firebug, your jQuery file is being loaded:

But the $ is being overwritten by something else:

---

What you should do is encapsulate the use of the $ variable with a function that invokes itself using the jQuery object as it's first actual argument:

(function ($) {

 // in this function, you can use the $ which refers to the jQuery object

}(jQuery));

"$ is not a function" is a very common error that you may face while working with jQuery. You can try any answers of given below:

(function($){
//your can write your code here with $ prefix
})(jQuery);

OR

jQuery(document).ready(function($){
//Write your code here
});

Basically this will allow our code to run and use the $ shortcut for JQuery.

Chances are your script is not initialized this way, you'll have to use Drupal.behaviors.YOURTHEMENAME

(function ($) {
Drupal.behaviors.YOURTHEMENAME = {
attach: function(context, settings) {

/*Add your js code here*/
alert('Code');

}

};
})(jQuery);