medium-4.js

function Base() {}
Base.prototype.foo = function() {return 'foo in Base';};
Base.prototype.bar = function() {return 'bar in Base';};

function Child() {}
Object.setPrototypeOf(Child, Base);
Object.setPrototypeOf(Child.prototype, Base.prototype);
Child.prototype.foo = function() {return 'foo in Child';};
Child.prototype.whiz = function() {return 'whiz in Child';};


var b = new Base;
var c = new Child;

console.log(b.foo()); // foo in Base
console.log(b.bar()); // bar in Base
console.log(c.foo()); // foo in Child
console.log(c.bar()); // bar in Base
console.log(c.whiz()); // whiz in Child