Assuming we wish to extend the redirectUrl component instead of replacing it completely, we can do so in a similar fashion. The entry in our requirejs-config.js remains the same, whereas the difference lies in how we edit our redirect-url.js file:

define([
 'jquery',
 'jquery/ui',
 'mage/redirect-url'
], function ($) {
 'use strict';
 $.widget('magelicious.redirectUrl', $.mage.redirectUrl, {
 /* Override of parent _onEvent method */
 _onEvent: function () {
 // Call parent's _onEvent() method if needed
 return this._super();
 }
 });
 return $.magelicious.redirectUrl;
});

Using the _super or _superApply is a jQuery widget way of invoking methods of the same name in the parent widget. While this approach works, there is a more elegant solution called mixins.

The Magento mixins for JS are much like its plugins for PHP. To convert to the mixin approach, we replace our requirejs-config.js with content, as follows.

var config = {
  config: {
    mixins: {
      'mage/redirect-url': {
        'Magelicious_Jsco/js/redirect-url-mixin': true
      }
    }
  }
};

Note, that this time we are using the full path 'mage/redirect-url' instead of the redirectUrl alias on the left side of the mapping, whereas the right side of mapping points to our mixin. The convention is to use the -mixing suffix on top of the original JS filename.

We then create <MODULE_DIR>/view/frontend/web/js/redirect-url-mixin.js with content, as follows:

define([
 'jquery'
], function ($) {
 return function (originalWidget) {
 $.widget(
 'magelicious.redirectUrl',
 originalWidget, {
 /* Redefined _onEvent method */
 _onEvent: function () {
 console.log('_onEvent via mixin'),
 // Call parent's _onEvent() method if needed
 return this._super();
 }
 }
 );
 return $.magelicious.redirectUrl;
 };
});

The example here might not do justice, as it merely looks more complex than the previous example of directly extending the widget. This is because we cannot simply do originalWidget._onEvent = function () { /* ... */ }; or originalWidget._proto._onEvent = function () { /* ... */ }; and thus override the widget method. Widget methods need to be overridden on the prototype, which, in our case, essentially means creating a new widget from the original.

If we were adding a mixin for a non-widget type of JS, such as Magento_Checkout/js/action/place-order, then the approach would be different, as shown in Magento_CheckoutAgreements/js/model/place-order-mixin .