JSFiddle - React, Tailwind, and code Playground

JavaScript

function Restaurant() {
}

Restaurant.prototype = (function() {
    var hamburgersBought = 0;

    return {
        constructor: Restaurant,

        // Returns total # of hamburgers that
        // customers bought, in *all* restaurants.
        buyHamburger: function () {
            return (hamburgersBought += 1);
        }
    };
}());

var mcDonalds = new Restaurant(),
    burgerKing = new Restaurant();

console.log(mcDonalds.buyHamburger());
console.log(burgerKing.buyHamburger());