prototypes.js

let obj = {};
console.log(Object.prototype); // [Object: null prototype] {}
console.log(Object.getPrototypeOf(obj)); // [Object: null prototype] {}

console.log(Object.prototype === Object.getPrototypeOf(obj)); // true
console.log(Object.prototype.isPrototypeOf(obj)); // true

Object.prototype.foo = 'Hey there!';
console.log(Object.prototype); // [Object: null prototype] { foo: 'Hey there!' }

console.log(obj.foo); // Hey there!