Simple node.js palindrome checker for the command line.

palindrome.js

const readline = require('readline');

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});

rl.question('Please enter potential palindrome: ', checkForPalindrome);

function checkForPalindrome(str)
{
    var resultText = "";

    // Only allow upper and lower case letters
    if (/^[a-zA-Z]+$/.test(str))
    {
        var result = true;
        resultText = "\"" + str + "\"" + " is a palindrome!";

        var strLowerCase = str.toLowerCase();

        for (var i = 0; i < str.length/2; i++)
        {
            var currentLetterLeft = strLowerCase[i];
            // Remember to substract 1 from length because of zero-indexing strings
            var currentLetterRight = strLowerCase[str.length-1-i];

            if (currentLetterLeft != currentLetterRight)
            {
                result = false;
                resultText = "\"" + str + "\"" + " is NOT a palindrome!";
                break;
            }
        }
    }
    else
    {
        resultText = "Only upper and lower case letters are allowed!";
    }
    console.log(resultText);
    rl.close();
}