JSFiddle - React, Tailwind, and code Playground

JavaScript

var Game = function(title) {
  this.title = title;
};

var zelda = new Game('Zelda - Ocarina of Time');
var smb = new Game('Super Mario Brothers')

Game.prototype.whoami = function() { 
    console.log( 'I am ' + this.title ); 
}; 

zelda.whoami();
smb.whoami();
console.log(smb.whoami === Game.prototype.whoami); // true

smb.whoami = function() {
  console.log('I am ' + this.title + ' - Second edition');
};

smb.whoami(); 

console.log(smb.whoami === Game.prototype.whoami); // false