정수 반전

reverseInt(15) === 51
reverseInt(981) === 189
reverseInt(500) === 5
reverseInt(-15) === -51
reverseInt(-90) === -9

1. 숫자를 문자열로 만듭니다 (split, reverse, join)

function reverseInt(n) {
    const reversed = n.toString().split('').reverse().join('');

    if (n < 0) {
        return parseInt(reversed) * -1;
    }

    return parseInt(reversed);
}

2. Math.sign 사용

function reverseInt(n) {
    const reversed = n.toString().split('').reverse().join('');

    return parseInt(reversed) * Math.sign(n);
}