ES6 (javascript)

[9033]

객체 동결

• 값이나 객체의 프로토타입이 변경되지 않게 함.
• 값을 변경하려고 할때 엄격 모드에는 오류로 처리.

  const obj = {
  name: 'sam'
  }
  Object.freeze(obj)
  obj.name = 'john'
  console.log(obj)

  const obj = {
  prop: 42,
  obj: {
  prop: 2
  }
  };
  console.log(obj);
  Object.freeze(obj);
  obj.prop = 99;
  obj.obj.prop = 99; // obj.obj의 프로토타입은 변경이 안되기 때문에 적용됨.
  console.log(obj);

[9033]

Assign Variables

const obj = {
  name: 'kim',
  age: 99,
  grade:{
    math: 'A',
    history: 'B'
  }
}

const {
  name = 'lee',
  age = 11,
  where = 'korea',
  grade: {
    math: mathGrade,
    history: historyGrade,
    science: scienceGrade = 'F'
  }
} = obj

console.log(name, age, where, mathGrade, historyGrade, scienceGrade)

[9033]

Function's Parameters

const fn = ({x:y = '1', t:z = '2'} = {t:'3'}) => console.log(y, z)
fn()
fn({})
fn({x:'4'})
fn({t:'5'})
fn({x:'6', t:'7'})

const arrFn = ([a = 7,b = 8,c = 9, , ...etc] = [1, 2, 3]) => console.log(a, b, c, etc)
arrFn()
arrFn([])
arrFn([10])
arrFn([11, 12, 13, 14, 15, 16])

[9033]

Getter / Setter

class MC {
  constructor(name){
    this._name = name;
  }
  get name(){
    return this._name;
  }
  set name(name){
    this._name = name;
  }
}

const mc = new MC('mc');

console.log(mc.name);
mc.name = 'mc one';
console.log(mc.name);

const temp = {
  1: null,
  _exist: false,
  get exist(){
    return this._exist
  },
  get w(){
    return this[1]
  },
  set w(val){
    this._exist = (val !== undefined && val !== null)
    this[1] = val
  }
}

console.log(temp.exist);
temp.w = 'mc two';
console.log(temp.exist);
console.log(temp.w);

const tempClass = new class MC2{
  constructor(){
    this['1'] = null
    this._exist = false
  }  
  get exist(){
    return this._exist
  }
  get w(){
    return this['1']
  }
  set w(val){
    this._exist = (val !== undefined && val !== null)
    this['1'] = val
  }
}

console.log(tempClass.exist);
tempClass.w = 'mc three';
console.log(tempClass.exist);
console.log(tempClass.w);