Prototypes in JavaScript

What is [[Prototype]]?
  Every object has a special hidden property called [[Prototype]] which is used to access that object's prototype.
  
  prototype object <- [[Prototype]] <- object
  
  [[Prototype]] is hidden and internal
  
  __proto__ can be used to set [[Prototype]]
  Fun fact:
    1. __proto__ is a historical getter/setter for [[Prototype]]
    2. Object.getPrototypeOf/Object.setPrototypeOf also get/set the prototype
    3. __proto__ can be either an object or null

E.g.

let animal = {
  eats: true
};

let rabbit = {
  jumps: true
};

rabbit.__proto__ = animal;

// we can find both properties in rabbit now:
alert( rabbit.eats ); // true
alert( rabbit.jumps ); // true

E.g. with new F()

let animal = {
  eats: true
};

function Rabbit(name) {
  this.name = name;
}

Rabbit.prototype = animal;

let rabbit = new Rabbit("White Rabbit"); //  rabbit.__proto__ == animal

alert( rabbit.eats ); // true

Setting Rabbit.prototype = animal
literally states the following: "When a new Rabbit is created, assign its [[Prototype]] to animal".



const obj = {};
obj.__proto === Object.prototype // true



Modern alternatives to __proto

const newObj = Object.create(proto[, descriptors]) // where "proto" is the [[Prototype]] of the newObj. Basically similar to const newObj = {}; newObj__proto = proto;
const newObj = Object.getPrototypeOf(obj)
const newObj = Object.setPrototypeOf(obj, proto)