Checks the number equals its reverse order

ReversedDigit.js

'use strict';

const numbertest = (digit) => {
    let reversedDigit = '';
    for (let $i = `${digit}`.length; $i >= 0; $i--) {
        reversedDigit += `${digit}`.charAt($i);
    }
    console.log(reversedDigit === digit);
};

numbertest(12321); //=> 12321 *true*
numbertest(12341); //=> 14321 *false*
numbertest(-11); //=> 11 *false*

const numbermathtest = (digit) => {
    let powerDigit = 1;
    let reversedDigit = 0;
    let whileloopbol = true;
    // Negative number test
    // digit = digit > 0 ? digit : digit * -1;
    while (whileloopbol) {
        let res = Math.floor(digit / powerDigit);
        if (res > 0) {
            powerDigit = powerDigit * 10;
            reversedDigit = (reversedDigit * 10) + res;
        } else {
            whileloopbol = false;
        }
    }

    console.log(reversedDigit === digit);
};

numbermathtest(3121); //=> 1213 *true*
numbermathtest(3132); //=> 2313 *false*
numbermathtest(8); //=> 8 *true*