7. 整数反转

/**
 * @param {number} x
 * @return {number}
 */
var reverse = function(x) {
    let rev = 0;
    while (x !== 0) {
        const digit = x % 10;
        x = ~~(x / 10);
        rev = rev * 10 + digit;
        if (rev < Math.pow(-2, 31) || rev > Math.pow(2, 31) - 1) {
            return 0;
        }
    }
    return rev;
};

var reverse = function(x) {
    let d = Array.from((Number(x)+‘‘));
    let minus = false;
    if(d[0] == ‘-‘){
        d.shift();
        minus = true;
    }
    let str = (minus?‘-‘:‘‘)+d.reverse().join(‘‘);
    let rev = Number(str);
    if (rev < Math.pow(-2, 31) || rev > Math.pow(2, 31) - 1) {
        return 0;
    }
    return rev;
}