JS) 생성자 new 없을때 붙여주는 에러핸들링 코드

new가 없을때 

function Car(key) {
  console.log(new.target);
  this.key = key;
}

let result1 = Car("Silver Car");
console.log(result1);
let result2 = new Car("Red Car");
console.log(result2);
-------
undefined
undefined
[Function: Car]
Car { key: 'Red Car' }

 

---

 

new를 추가하는 코드 

function Car(key) {
  if (!new.target) {
    return new Car(key);
  }
  this.key = key;
}

let result1 = Car("Silver Car");
console.log(result1);  //Car { key: 'Silver Car' }
let result2 = Car("Red Car");
console.log(result2);  //  Car { key: 'Silver Car' }