Are you sure you should generate all those objects and arrays?
And the second code additionally looks quite complex.

Testing whether a number is palindromic is actually quite simple:

function isPalindrome(num) {
    if (num < 0 || num != 0 && num % 10 == 0) {
        return false
    }
    var rev = 0
    while (rev < num) {
        rev = rev * 10 + num % 10
        num /= 10
    }
    return rev == num || rev / 10 == num
}

Are you sure you should generate all those objects and arrays?
And the second code additionally looks quite complex.

Testing whether a number is palindromic is actually quite simple:

function isPalindrome(num) {
    if (num % 10 == 0) {
        return num == 0
    }
    var rev = 0
    while (rev < num) {
        rev = rev * 10 + num % 10
        num /= 10
    }
    return rev == num || rev / 10 == num
}

Are you sure you should generate all those objects and arrays?
And the second code additionally looks quite complex.

Testing whether a number is palindromic is actually quite simple:

function isPalindrome(num) {
    var rev = 0
    while (rev < num) {
        rev = rev * 10 + num % 10
        num /= 10
    }
    return rev == num || rev / 10 == num
}

Are you sure you should generate all those objects and arrays?
And the second code additionally looks quite complex.

Testing whether a number is palindromic is actually quite simple:

function isPalindrome(num) {
    if (num < 0 || num != 0 && num % 10 == 0) {
        return false
    }
    var rev = 0
    while (rev < num) {
        rev = rev * 10 + num % 10
        num /= 10
    }
    return rev == num || rev / 10 == num
}