palindrome_dm.js

'use strict'; // avoid ambiguity and sloppy errors

/**
 * Tests wether or not a given string is a Palindrome
 * @param {string} stringToTest - the string to test.
 * @returns {boolean}
 */
function isPalindrome(stringToTest) {
  var start = 0;

  // make sure we have a string.
  if (typeof stringToTest !== "string")
    return false;

  stringToTest = stringToTest
      .toLowerCase()
      .replace(/\W+/g, '');

  var end = stringToTest.length - 1;

  // compare characters from outside in. stop when we get to the middle.
  while (start < end) {
    if (stringToTest[start++] !== stringToTest[end--])
      return false;
  }

  // if we get here, it's a palindrome
  return true;
}

// tests (should be in a seperate file using a test framework)
console.log(isPalindrome("something that is not a palindrome") + " = false");
console.log(isPalindrome("something that is \n not a palindrome") + " = false");
console.log(isPalindrome("race \n car") + " = true");
console.log(isPalindrome("") + " = true");
console.log(isPalindrome("  ") + " = true");
console.log(isPalindrome("1221") + " = true 1221");
console.log(isPalindrome("0") + " = true");
console.log(isPalindrome("racecar") + " = true");
console.log(isPalindrome("No 'x' in Nixon!") + " = true");
console.log(isPalindrome("~~!~!~") + " = true + warn");
console.log(isPalindrome("Momsie") + " = false");
console.log(isPalindrome(12) + " = warn + false");
console.log(isPalindrome(undefined) + " = warn + false");
console.log(isPalindrome(null) + " = warn + false null");