Magento 2: PrototypeJS Still Lurks

I was investigating Magento 2’s TinyMCE implementation the other day, and came across this

#File: vendor/magento//magento2-base/lib/web/mage/adminhtml/wysiwyg/tiny_mce/setup.js
define([
    'jquery',
    'underscore',
    'tinymce',
    'mage/translate',
    'prototype',
    'mage/adminhtml/events',
    'mage/adminhtml/browser'
], function(jQuery, _, tinyMCE) {

    tinyMceWysiwygSetup = Class.create();    
    //...
});

The TinyMCE RequireJS setup module was referencing a Class object – but there was no such object imported in the list of module dependencies.

I was flummoxed as to where this came from for a few minutes – did I miss some modern javascript addition where classes are something more than an alias to a function constructor?

Then I looked again at the list of RequireJS dependencies and saw this

'prototype',

A quick search through the requirejs-config.js files revealed this was an alias for the legacy-build.min module

vendor/magento/module-theme/view/base/requirejs-config.js
45:        "prototype": "legacy-build.min",

and peek at that module’s source revealed –

#File: vendor/magento/magento2-base/lib/web/legacy-build.min.js
var Prototype={Version:"1.7",Browser:...

a minified version of PrototypeJS, which defines a globally available Class object.

As a programmer, I actually like Javascript. It’s a small language, with an interesting non-class based object system, and powerful first-class-functions that support closure.

As a developer though, dealing with the variety of different userland created object systems within the same project can be a bit maddening.