drupal.js is loading before jquery.js

Question

I have face this problem often in my drupal site. The drupal.js file is loading before jquery.js, so i get the "uncaught jQuery is not defined" error.

I have been using memcached also in my site.

But I can fix the error by the following steps

1. Restart memcached
2. Restart Apache
3. Cache clear
4. Run the cron

After doing the steps the jQuery is loading properly.

Now, i want to know the reason why the drupal.js loading before jquery.js?

FYI : This is happening, When I enable/disable any modules/features through UI

Answer 1

May be because of cache that might cause

1. Check if you installed jquery_update module

2. in themes info check if there you have declared jquery

   3.check if in any module hook_init() you are adding your js with weight.

if you install jquery update module you dont need to add jquery plugin in info file

if you have any clarification regarding the js weight and so on read the following links will be helpful

https://www.drupal.org/node/756722

https://www.drupal.org/node/304255

Answer 2

Use hook_js_alter see the below example code.

function MODULENAME_js_alter(&$js) {
drupal_add_js('mise/drupal.js', 'external');
drupal_add_js('mise/jquery.js', 'external');    
}

Answer 3

Thanks @Clive, you comment help more to find out the issue.

In my case, we have used the drupal_add_js outside of the functions/hooks without any conditions as the following code,

<?php

// Adds the custom css file into the module.
$module_path = drupal_get_path('module', 'kf_book_quiz');
drupal_add_js($module_path . '/kf_book_quiz.js');
drupal_add_css($module_path . '/kf_book_quiz.css');
drupal_add_css($module_path . '/kf_book_quiz_rwd.css');
module_load_include('inc','quiz','quiz.admin');

/**
 * Implements hook_init()
 */
function kf_book_quiz_init() {

}

It is not a proper way to add the js into module. This would break the js queue structure. We should add js only where it is needed, we could use hook_preprocess_page to add js for needed place with conditions.