JSFiddle - React, Tailwind, and code Playground

JavaScript

var myProto = {
    foo: 123
};

var myOtherProto = {
    foo: 456
};

var myCtor = function() {};

myCtor.prototype = myProto;


var myInstance = new myCtor();

document.write(myInstance.foo);

myInstance.__proto__ = myOtherProto;

document.write(myInstance.foo);