Overriding Drupal.ajax.prototype is not working

Question

I am trying to override Drupal.ajax.prototype.beforeSend like this:

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

The file that contains the code is listed below core's ajax.js in the page's source, yet it's the console.log I put inside core's ajax.js beforeSend that is showing up.

What else is to it? Has anything been changed in Drupal? Using version 9.3. Can't override any of those functions.

Answer 1

There are two javascript objects:

1. Drupal.ajax
2. Drupal.Ajax

You have to override the prototypes in Drupal.Ajax. For each Ajax object declared in Drupal settings an instance of it will then be stored in Drupal.ajax.instances.