Javascript Recursive Function is Palindrome

function isPalindromeRecursive(word) {
    return isPalindromeHelper(word, 0, word.length - 1);
}

function isPalindromeHelper(word, beginPos, endPos) {
    if (beginPos >= endPos) {
        return true;
    }//from w  w  w  .j ava2  s .co  m
    if (word.charAt(beginPos) != word.charAt(endPos)) {
        return false;
    } else {
        return isPalindromeHelper(word, beginPos + 1, endPos - 1);
    }
}

isPalindromeRecursive('hi'); // false
isPalindromeRecursive('iii'); // true
isPalindromeRecursive('ii'); // true
isPalindromeRecursive('level'); // true
isPalindromeRecursive('racecar'); // true