Add js library to custom ckeditor4 plugin

How can an external JS library be integrated into Drupal for use within a custom Ckeditor4 plugin?

My custom plugin needs to set a javascript cookie each time I click on the plugin icon and unset when I close the plugin dialog.

I attempted to use JQuery which didn't work and when I googled the issue, I found a post saying the jquery-cookie is being replaced with js-cookie.

I attempted to install js-cookie and tried the following example:

(function ($, Drupal, drupalSettings, CKEDITOR, Cookies) {
    Cookies.set('foo', 'bar')
})(jQuery, Drupal, drupalSettings, CKEDITOR, window.Cookies);

but got the following error:

Uncaught TypeError: Cannot read properties of undefined (reading 'set')

I'm not sure if it's becuase of the way I attached the JS-Cookie library.

The following are the steps I took to attach the library.

I used a composer plugin to require js-cookie into my custom module. My composer.json is as follows:

{
    "name": "my/module",
    "description": "Custom module ckeditor4 plugin",
    "authors": [
        {
            "name": "my-name",
            "email": "[email protected]"
        }
    ],
    "repositories": [
        {
            "type": "composer",
            "url": "https://asset-packagist.org"
        }
    ],
    "extra": {
        "installer-types": [
            "npm-asset",
            "bower-asset"
        ],
        "installer-paths": {
            "libraries/asset-packagist/{$name}": [
                "type:npm-asset",
                "type:bower-asset"
            ]
        }
    },
    "require": {
        "oomphinc/composer-installers-extender": "^2.0",
        "npm-asset/js-cookie": "^3.0",
        "npm-asset/cookie": "^0.5.0"
    }
}

Which downloads the required library into the following directory structure from the root of the module code base:

libraries
├── asset-packagist
│   ├── cookie
│   └── js-cookie

At this point I am able to create an entry in my_module.libraries.yml using the following:

js-cookie:
  js:
    libraries/asset-packagist/js-cookie/dist/js.cookie.min.mjs: {}
  dependencies:
    - core/jquery
    - core/drupalSettings

. . . and attach the library to a form using the following hook_form_alter implementation:

function my_module_form_alter(&$form, &$form_state, $form_id) {
  $form['#attached']['library'][] = 'my_module/js-cookie';
}

And I confirmed the js-cookie library is sucessfully loaded in the HTML:

I think you should delete these lines from your library file.

js-cookie:
  js:
    libraries/asset-packagist/js-cookie/dist/js.cookie.min.mjs: {}
  dependencies:
    - core/jquery
    - core/drupalSettings

You try need to replace the used library core/jquery.cookie to core/js-cookie.

my_module.libraries.yml

my_library:
  js:
    js/my_library.js: {}
  dependencies:
    - core/drupal
    - core/js-cookie
    - core/drupalSettings
    - core/jquery

js/my_library.es6.js

(($, Drupal, drupalSettings, CKEDITOR, cookies) => {
  Drupal.behaviors.myModule = {
    attach: () => {
      // Set a cookie.
      cookies.set('cutest', 'red panda');
      // Retrieve a cookie.
      const cutest = cookies.get('cutest');
      // Remove a cookie.
      cookies.remove('cutest');
      // Store and retrieve as a JSON object. Use of the getJSON method should be avoided as that will be deprecated in js-cookie 3.0.0.
      cookies.set('cutest', JSON.stringify({ animal: 'red panda' }));
      const cutest = JSON.parse(cookies.get('cutest'));
    },
  };
})(jQuery,Drupal, drupalSettings, CKEDITOR,window.Cookies));

Here is the official documentation with an anchor to the part that explain how to use js-cookie: https://www.drupal.org/node/3104677