Palindromes

A palindrome is a word that it is spelled the same forward than backward. For example "ROTOR"

Pseudo-code

1. If string has no letters or just one letter then it is a palindrome.
2. Otherwise, compare first and last letters of the string. If they differ it is not a palindrome.
3. Keep doing the same until you end up with one letter or 0

Implementation

// Returns the first character of the string str
var firstCharacter = function(str) {
    return str.slice(0, 1);
};

// Returns the last character of a string str
var lastCharacter = function(str) {
    return str.slice(-1);
};

// Returns the string that results from removing the first
//  and last characters from str
var middleCharacters = function(str) {
    return str.slice(1, -1);
};

var isPalindrome = function(str) {
    // base case #1
    if (str.length <= 1) {
        return true; 
    }
    // base case #2
    if (firstCharacter(str) !== lastCharacter(str)) { 
        return false; 
    }
    // recursive case
    return (firstCharacter(str) === lastCharacter(str)) && isPalindrome(middleCharacters(str));
};

var checkPalindrome = function(str) {
    println("Is this word a palindrome? " + str);
    println(isPalindrome(str));
};

checkPalindrome("a");
Program.assertEqual(isPalindrome("a"), true);
checkPalindrome("motor");
Program.assertEqual(isPalindrome("motor"), false);
checkPalindrome("rotor");
Program.assertEqual(isPalindrome("rotor"), true);