interview.js

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

/**
 * Tests whether or not a given string is a Palindrome
 * @param {string} stringToTest - the string to test.
 */
function isPalindrome(stringToTest) {
    if (typeof stringToTest !== "string") {
        throw new TypeError("isPalindrome() expected a string, but got " +
            Object.prototype.toString.call(stringToTest) + " instead!");
    }

    var normalizedString = stringToTest
                    .toLowerCase()
                    .replace(/\W/g, ''); // remove non-word characters

    if (normalizedString.length === 0) {
        return true; // an empty string is a palindrome.
    }

    return normalizedString === normalizedString.split('').reverse().join('');
}

// tests (should be in a separate 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 + warn");
console.log(isPalindrome("  ") + " = true + warn");
console.log(isPalindrome("1221") + " = true");
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)); // blow up
console.log(isPalindrome(undefined)); // blow up
console.log(isPalindrome(null)); // blow up