JSFiddle - React, Tailwind, and code Playground

JavaScript

function A(){
this.a = 10;
}

A.prototype.b = 1;

o1 = new A();

o2 = new A();

o1.b = 10;
o2.b = 20;

document.body.innerHTML += o1.b + " " + o2.b + "<br>";

document.body.innerHTML += o1.__proto__.b + "<br> ";
document.body.innerHTML += o2.__proto__.b + "<br> ";