class-07(code sample)

//javascript "this"

//inside of the function (functional context)
//outside of function (global context)

//window obj(global context) -Don't use
console.log(this)
;('use strict')
function whatIsThis() {
  //In strict mode  this indicates undefined otherwise widow object
  console.log(this)
}

whatIsThis() //plain function call (window)

const calculator = {
  num1: 2,
  num2: 3,
  add() {
    console.log(this.num1 + this.num2)
    // console.log(this)
    const $this = this
    function multiply() {
      console.log($this.num1 * $this.num2)
    }
    multiply()

    const division = () => {
      console.log(this.num2 / this.num1)
    }
    division()

    function subtraction(a, b) {
      console.log(this, a, b)

      console.log(this.num2 - this.num1)
    }
    return subtraction
  }
}
// console.log(calculator.add())

const subs = calculator.add()
const result = subs.bind(calculator, 1, 2) //don't call the function , just bind the 'this'

result.apply('blabla') //don't work

console.log(result())

console.log(subs)

// console.log(subs.call(calculator, 1, 2))
// console.log(subs.apply(calculator, [1, 2]))

//binding this to result

//result

//constructor function (this)
//create empty object
//return (this) object be default
function Construct() {
  this.number1 = 1
  this.number = 2
  // console.log(this)
}

const numbersObj = new Construct()
console.log(numbersObj)

//this summary
//1. global context indicates window obj
//2. How you call the function will define How this indicates inside this function
//3.plain function call -window object
//(in strict mode undefined)
//array function doesn't have own this binding(parent context defines 'this')
//4. calling methods as a part of object this will indicate the object
//5. constructor function this indicates empty object

// const samim = {
//   firstName: 'samim',
//   lastName: 'hasan',
//   fullName() {
//     return this.firstName + this.lastName
//   }
// }

// const khalil = {
//   firstName: 'khalil',
//   lastName: 'hasan',
//   fullName() {
//     return this.firstName + this.lastName
//   }
// }
//factory function
// function person(firstName, lastName) {
//   return {
//     firstName,
//     lastName,
//     fullName() {
//       return this.firstName + this.lastName
//     }
//   }
// }

// const samim = person('samim', 'Hasan')
// const khalil = person('Khalil', 'Hasan')
// console.log(khalil)

function Person(firstName, lastName) {
  this.firstName = firstName
  this.lastName = lastName
  this.fullName = function () {
    return this.firstName + this.lastName
  }
}
const samim = new Person('samim', 'Hasan')
const khalil = new Person('Khalil', 'Hasan')
console.log(samim.fullName())
console.log(khalil)

//scope
//var, let, const
//var (global scope, functional scope)
//let, const (global scope, block scope{})

//scope , scope chian

// var greet = 'Hello'

// function showGreet() {
//   // var greet = 'Hola'
//   // console.log(greet)
//   function showHello() {
//     console.log(greet)
//   }
//   showHello()
// }

// showGreet()
// console.log(greet)

// const num1 = 0

// {
//   const num2 = 2
//   console.log(num1)
//   {
//     const num3 = 3
//     console.log(num3)
//     console.log(num2)
//   }
// }

// console.log(num1)
//closure (scope)

function add() {
  const b = 5
  const a = 3
  function subtraction() {
    console.log(b - a)
  }
  return subtraction
}

const result2 = add()
console.log(result2())