JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">Hello, world<br><br></div>

JavaScript

var Square = function () {
    var side;
    this.setSide = function(s) {
        side = s
    }
    this.getSide = function() {
        return side;
    }
}
Square.prototype.u = 'px';

var red = new Square();
var orange = Object.create(red);

red.setSide(100);

var $container = $('#container');

$container.append('orange.getSide(): ' + orange.getSide() + '<br>');
$container.append('red.getSide(): ' + red.getSide() + '</br><br>');
$container.append('<i>Now we call orange.setSide(99)...</i><br></br>');

orange.setSide(99);

$container.append('orange.getSide(): ' + orange.getSide() + ' <i>...as expected.<br></i>');
$container.append('red.getSide(): ' + red.getSide() + '!? <i>Why does the call to orange.setSide(99) affect the side length of the parent?</i></br>');