let a = Object.create(null); // doesn't have a prototype
let b = { }; // has Object.prototype

var User = function(name) {
    this.name = name;
    /* jshint proto: true */
    this.__proto__ = b;
    // User.prototype.constructor = User // This constructor creates automatically,
    // but it could be easyly overriden with User.prototype = {}
};

// This approach doesn't override default prototype's constructor property
User.prototype.hello = function(who) {
    console.log("Hello, " + who.name);
};

var vasya = new User("Вася");   // Has __proto__ = User.prototype
var petya = new User("Петя");
petya.hit = () => "Hit";


vasya.hello(petya);
console.log(petya.hit());
console.log(Object.getPrototypeOf(petya));