LeetCode 7. Reverse Integer (javascript)

Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range [-2³¹, 2³¹ - 1], then return 0.

Assume the environment does not allow you to store 64-bit integers (signed or unsigned).

Example 1:

Input: x = 123
Output: 321

Example 2:

Input: x = -123
Output: -321

Example 3:

Input: x = 120
Output: 21

Example 4:

Input: x = 0
Output: 0

Constraints:

-2³¹ <= x <= 2³¹ - 1

Solution:

/**
 * @param {number} x
 * @return {number}
 */

var reverse = function(x) {
    const str      = "" + Math.abs(x);   // convert absolute value to string
    const reversed = str.split("")       // get array of digit characters
                   .reverse()            // reverse it
                   .join("");            // join into string again;
    const num      = parseInt(reversed); // convert to integer
    const revNum = Math.sign(x) * num;   // multiple the sign
    // if out of range return 0
    if (revNum < Math.pow(-2, 31) || revNum > Math.pow(2, 31) - 1) return 0;
    return revNum;
}