If you are using more than one JS file, you should be using AMD, as it will ensure that no one script runs before its dependencies are loaded.

If the external file is an exportable AMD module, you should register it:

// Register the script for synchronous loading in your start.php
elgg_register_js('external_script_name', $external_url);

// Load the script where you need it
elgg_load_js('external_script_name');

Most scripts these days come as AMD module, e.g. moment.js, so you can register them and require them in your script:

// Define the module
elgg_define_js('moment', [
   'src' => $cdn_url,
   'exports' => 'moment',
]);

// In your AMD module
define(function(require) {
   var moment = require('moment');
   var $ = require('jquery');
});

You shouldn't need to know the location of jQuery. If you do, then you are doing something wrong.

Thanks a lot

Depends on how the plugins manage the requests.
http://learn.elgg.org/en/stable/guides/events-list.html

Thanks a lot. 

I am using elgg_register_event_handler('create', 'friendrequest', 'my_function') for handling friend request and everything work perfectly.

But I dont know which event I should used when the following action is performed:

• When "Friend request" is Approved or Declined.

Best regard 

Look at the action and see what happens to the relationship when the request is approved or declined. Maybe the plugin triggers additional events.

Wrap your code in elgg_set_ignore_access

Thanks veryrthing is working now.

In case you don't know, the invisible group can't be loaded for a user who can't see it, so it was passing false into your function. That function turns off the access limitations so the code can see every (enabled) entity, annotation, etc.