Prototypes and Classes

prototypes-classes.js

// Functional Instantiation
// the weakness of this pattern is that whenever we create
// a new person, we have to re-create all the methods in memory, 
// which is not cool..
function Person (name, energy) {
  let person = {}
  person.name = name
  person.energy = energy
  
  person.eat = function (amount) {
    console.log(`${this.name} is eating !`)
    this.energy += amount
  }
  
  return person
}
const breno = Person('Breno', 8)
breno.eat(5) // Breno is eating !

---

// Functional Instantiation + Shared Methods
// every time we create a new person, we move them to their
// own object, then we can have each person reference that object
const personMethods = {
  eat(amount) {
    console.log(`${this.name} is eating !`)
    this.energy += amount
  }
} 

function Person (name, energy) {
  let person = {}
  person.name = name
  person.energy = energy
  person.eat = personMethods.eat
  
  return person
}

const rodrigo = Person('Rodrigo', 7)
rodrigo.eat(5) // Rodrigo is eating !

---

// 
// Prototypal Instantiation
function Person (name, energy) {
  let person = Object.create(Person.prototype)
  person.name = name
  person.energy = energy
  
  return person
}
Person.prototype.eat = function (amount) {
  console.log(`${this.name} is eating !`)
  this.energy += amount
}
const leo = Person('Leo', 5)
leo.eat(5) // Leo is eating !

// Object.Create allows to create an object and whenever there's a failed property
// on that object, it can consult another object to see if that other
// object has that property.
//
// ex.:
// const parent = {
//  name: 'Ana',
//  nationality: 'Brazilian'
// }
//
// const child = Object.create(parent)
// child.name = 'Matheus'
//
// console.log(child.name)  // Matheus
// console.log(child.nationality) // Brazilian

---

// Prototypes with 'new' keyword
function PersonWithNew (name, energy) {
  // under the hood, when the 'new' keyword is added,
  // it runs Object.create() ans return it.
  this.name = name
  this.energy = energy
}
PersonWithNew.prototype.eat = function (amount) {
  console.log(`${this.name} is eating !`)
  this.energy += amount
}
const allan = new PersonWithNew('Allan', 9)
allan.eat(5) // Allan is eating !

---

// Classes (ES6)
// in JavaScript, classes are just 'sugar sintax' of prototypes 
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes
class PersonClass {
  constructor(name, energy) {
    this.name = name
    this.energy = energy
  }
  eat() {
    console.log(`${this.name} is eating !`)
    this.energy += amount
  }
}
const igor = new PersonClass('Igor', 2)
igor.eat(5) // Igor is eating !