I used drupal_add_js() to add a jquery plugin, but there is an error TypeError: $ is undefined at console of firebug. So how should I add the js?

  • try replacing the $ with jQuery tag. Something like jQuery('#some-id').hide(); instead of $('#some-id').hide(); and we can carry on from there.
    – saadlulu
    Dec 24, 2012 at 7:09

1 Answer 1


I think you'd find this article in the Drupal documentation relevant and helpful.

The solution is to wrap your custom Javascript code within a closure as shown below:

(function($) {
  // Your Javascript code goes here

Javascript files from all Drupal core modules follow this convention. So, you can look them up for reference.

I'm not really sure but either before/after some version of jQuery, the $ was a global alias for the jQuery object itself and could be used directly without the closure but was later removed as it conflicted with other libraries.

  • It is the problem of third part library, it used $ without the closure. Dec 24, 2012 at 7:39

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