SOURCE

var reverse = function(x) {
    var temp = x.toString();
    var sign = 1;
    const INT_MAX = Math.pow(2,31) -1;
    const INT_MIN = -1 * Math.pow(2,31);
    if (temp[0] == '-') {
        sign = -1;
        temp = temp.substr(1);
    }
    temp = temp.split("").reverse().join("");
    if (temp*sign > INT_MAX || temp*sign < INT_MIN) {
        return 0;
    }
    return temp*sign;
};
console.log(reverse("-123"));