JSFiddle - React, Tailwind, and code Playground
HTML
<input type="number" id="parent-class-created-count">
<p>Should be 3!</p>
JavaScript
var parentClassCreatedCount = 0;
function Parent() {
parentClassCreatedCount++;
}
function Child() {
Parent.apply(this, arguments);
}
Child.prototype = new Parent();
var a = new Parent();
var b = new Child();
var c = new Child();
document.getElementById('parent-class-created-count').value = parentClassCreatedCount;