Prototypes in JavaScript

Here is the summary of JavaScript's prototypes from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Inheritance_and_the_prototype_chain.

• In JS, there is no implementation of a class per se
  • the ES2015's class keyword is just a syntactical sugar
• When it comes to inheritance, JS only has one construct: objects.
• An object has
  • private prototype: a link to another object
  • own properties: other properties
• An object a's prototype is denoted as a.[[Prototype]]
• You can access the prototype of an object a (a.k.a. a.[[Prototype]])by
  • Object.getPrototypeOf(a)
  • Object.setPrototypeOf(a)
• Note that func.prototype is a different beast!
  • It specifies the [[Prototype]] to be assigned to all instances of objects created by the given function when used as a constructor.

const f = function() {
	this.a = 1;
	this.b = 2;
};

const o = new f(); // {a: 1, b: 2}

f.prototype.b = 3;
f.prototype.c = 4;

Object.getPrototypeOf(Object.getPrototypeOf(o)).d = 5

Object.setPrototypeOf(Object.getPrototypeOf(o), {e:6})