How to override Drupal.ajax.prototype.beforeSend?

Question

I need to add my own little if's and checks in 3 functions inside

misc/ajax.js (
  Drupal.ajax.prototype.beforeSend,
  Drupal.ajax.prototype.success,
  Drupal.ajax.prototype.error
)

How can I override them in my module? I can't find a manual and it's not in Examples for Developers. Sorry if it seems a dumb question, but I'm a php developer - I can work with js, but I'm not so fluent with it.

• Can I simply write it in my module's js file?
• If 2 or 3 modules needs to modify them, how to avoid conflicts?

Answer 1

Drupal.ajax.prototype.beforeSend and the others are just variables that happen to have functions assigned to them. As long as your code appears in the page build after the original function implementations, you you should be able to just override what's already there:

(function($) {
  // In mymodule.js, which appears after ajax.js in the page build
  Drupal.ajax.prototype.beforeSend = function(xmlhttprequest, options) {
    // Replacement code.
  }
})(jQuery);

Answer 2

This might be a better way:

(function ($) {
  // Drupal's core beforeSend function
  var beforeSend = Drupal.ajax.prototype.beforeSend;
  // Add a trigger when beforeSend fires.
  Drupal.ajax.prototype.beforeSend = function(xmlhttprequest, options) {
    beforeSend.call(this, xmlhttprequest, options);
    $(document).trigger('beforeSend');
  }
})(jQuery);

https://www.drupal.org/node/1372840