sag1v

const playerFunctions = {
  setScore(newScore) {
    this.score = newScore;
  }
}

function createPlayer(userName, score) {
  const newPlayer = Object.create(playerFunctions);
  newPlayer.userName = userName;
  newPlayer.score = score;

sag1v

function Player(userName, score){
  this = {} // ⚠️ done by JavaScript
  this.__proto__ = Player.prototype // ⚠️ done by JavaScript

  this.userName = userName;
  this.score = score;

  return this // ⚠️ done by JavaScript
}

sag1v

class Player {
  constructor(userName, score) {
    this.userName = userName;
    this.score = score;
  }
}

sag1v

double.hasOwnProperty('name')

sag1v

class Player {
  constructor(userName, score) {
    this.userName = userName;
    this.score = score;
  }

  setScore(newScore) {
    this.score = newScore;
  }
}

sag1v

Player {
  userName: "sag1v",
  score: 700,
  __proto__: Player.prototype
}

Player {
  userName: "sarah",
  score: 900,
  __proto__: Player.prototype

sag1v

const playerFunctions = {
  setScore(newScore) {
    this.score = newScore;
  }
}

function createPlayer(userName, score) {
  const newPlayer = Object.create(playerFunctions);
  newPlayer.userName = userName;
  newPlayer.score = score;

sag1v

function Player(userName, score){
  this.userName = userName;
  this.score = score;
}

Player.prototype.setScore = function(newScore){
  this.score = newScore;
}

const player1 = new Player('sag1v', 700);

sag1v

function Player(username, score){

  if(!(this instanceof Player)){
    throw new Error('Player must be called with new')
  }

  // ES2015 syntax
  if(!new.target){
    throw new Error('Player must be called with new')
  }

sag1v

Player {
  userName: "sag1v",
  score: 700,
  __proto__: Player.prototype {
    setScore: ƒ
  }
}

PaidPlayer {
  userName: "sarah",