Reverse integer and determine overflow in JavaScript - LeetCode solution

reverse-int.js

/**
 * @param {number} x
 * @return {number}
 */
var reverse = function(x) {
    let a = x.toString().split('')
    let num;
    if(a[0] == '-') {
        let c = a.shift()
        num = parseInt(c +a.reverse().join(''))
    } else {
       num = parseInt(a.reverse().join(''))
    }
    
    if(Math.abs(num) > Math.pow(2, 31)) {
        num = 0;
    }
    
    return num
};

var reverse = function(x) {
var myInt = Math.abs(x).toString().split('').reverse().join('');

var num = +myInt
return (x<0 ?  -1:1) * num

};
after submission my code status shows wrong answer on leetcode what is wrong with code please help me!