Spread & Rest Operators

Spread ... : 배열의 원소나 객체의 프로퍼티를 나누는데 사용

const numbers = [1,2,3];
const newNumbersSpread = [...numbers, 4];

console.log(newNumbers); // [1,2,3,4]

const newNumbers = [numbers, 4];
console.log(newNumbers); // [[1,2,3],4]

const person = {
  name: 'Max'
};

const newPerson = {
  ...person,
  age: 28
}

console.log(newPerson); 
/**[object Object] {
  age: 28,
  name: "Max"
}
**/ 

Rest : 배열 합칠 때 사용

const filter = (...args) => {
  return args.filter(el => el === 1);
}
 
console.log(filter(1,2,3,)); // [1]