N-th Digit of Number

/* Write a JavaScript function findNthDigit(arr) that accepts as a parameter an array of two numbers
num and n and returns the n-th digit of given decimal number num counted from right to left.
Return undefined when the number does not have n-th digit. Write a JS program nthDigitOfNumber.js
that invokes your function with the sample input data below and prints the output at the console. */

"use strict";

function findNthDigit(arr) {
    var n;
    if (arr[0] % 1 === 0) n = parseInt(arr[0]);

    var num = parseFloat(arr[1]);
    if (n == undefined || num !== Number(num) || !n) {
        return undefined + ' - Wrong Input arguments!!!';
    }

    num = Math.abs(num);
    while (num % 1 != 0) {
        num *= 10;
    }

    var numStr = num.toString(10);
    if (n > numStr.length) {
        return undefined + ' - The number doesn’t have ' + n + ' digits!';
    }

    return numStr.charAt(numStr.length - n);
}

console.log(findNthDigit([1, 6]));
console.log(findNthDigit([2, -55]));
console.log(findNthDigit([6, 923456]));
console.log(findNthDigit([3, 1451.78]));
console.log(findNthDigit([6, 888.88]));
console.log(findNthDigit([0, 321]));
console.log(findNthDigit(['2', '258.12']));