[함수] 반환 및 종료

function hello(){
	return 'Helllo!'
}
console.log(hello);

function plus(num){
	return  num + 1;
}

console.log(plus(2)); //3
console.log(plus(7)); //8
console.log(plus()); // NaN = undefined + 1;

function plusV2(num){
  if(type num !== 'number'){
  	console.log('숫자를 입력해주세요!')
    return 0;
  }
  return num + 1;
}
console.log(plusV2()) // 숫자를 입력해주세요! 0