__proto__ behavior

proto1.js

var a = { hello: 'world' };
var b = {};

// has no own property "hello"
console.log(b.hello); // undefined

// set __proto__ to b, so "hello" will resolve
b.__proto__ = a;
console.log(b.hello); // hello

// remove __proto__ and sever the underlying magic.
b.__proto__ = null;
console.log(b.hello); // undefined

// now we cant set it.
b.__proto__ = a;
console.log(b.hello); // undefined