function App() {
  const [state, setState] = useState(0);

  const handleClick = () => {
    setState(state + 1);
    setState(state + 1);
    setState(state + 1);
  };

  return (
    <div className="App">
      <p>{state}</p>
      <button
        onClick={() => {
          handleClick();
        }}
      >
        +3
      </button>
    </div>
  );
}

export default App;

function returnX(){
    return 'x';
}

const x = returnX()
console.log(typeof x) // string

----------------------------------------------

function returnX() {
    let x = 'x';
    return function returnY() {
        return x + 'y';
    }
}

const x = returnX()
console.log(typeof x) // function => return 값이 함수 덩어리이기 때문에

const x = returnX()();
console.log(typeof x) // string
function sum(num1) {
    return function (num2) {
        return num1 + num2;
    };
}

const sum5 = sum(5); // 숫자5가 계속 바인딩되어 있는 상태
console.log(sum5(10)); // 15

function privateData() {
    let temp = 'a';
    return temp;
}

const result = privateData(); // privateData를 실행시켜야만 temp값을 알 수 있다.
console.log(result);

-------------------------------------

function privateData() {
    let temp = 'a';
    return {
        value: () => {
            return temp;
        },
        changeValue: (newVal) => {
            temp = newVal;
        }
    };
}

const private = privateData();
console.log(private.value()); // a
private.changeValue('b');
console.log(private.value()); // b

function Person(name, age) {
    this.name = name;
    this.age = age;
}

class Person {
    constructor(name, age) {
        this.name = name;
        this.age = age;
    }
}

function Person(name, age) {
	this.name = name;
	this.age = age;
}

class Paerson {
	constructor() {

	}
}

const one = new Person('one', 1);
const two = new Person('two', 2);

console.log(one.constructor); // [Function: Person]
console.log(two.constructor.name); // Person