isPalindrome Function in Javascript

isPalindrome.js

/** 
 * Checks whether a supplied string is a palindrome,
 * meaning it is spelled the same forwards and backwards
 * 
 * @param {String} - The string to check 
 * @return {Boolean} - True, if the string is a palindrome. False, if it is not.
 */
function isPalindrome(stringToCheck) {
  
  /**
   * Reverses a string and returns it
   * 
   * @param {String} - The string to reverse
   * @return {String} - The reverse of the supplied string 
   */
  function reverseString(stringToReverse) {
    //Split string characters into an array and mark its start and end indexes
    var 
      chars = stringToReverse.split(''),
      startIndex = 0, 
      endIndex = chars.length - 1
    ;
    //Step from the beginning and end of the array 
    //toward the middle, swapping the characters at the start 
    //and end indexes
    while (startIndex < endIndex) {
      var left = chars[startIndex];  
      chars[startIndex] = chars[endIndex];
      chars[endIndex] = left;
      
      startIndex++;
      endIndex--;
    }
    return chars.join('');
  }
 //If a word is the same forwards and backwards, it is a palindrome 
 return (stringToCheck === reverseString(stringToCheck));
}

var words = ["wakka", "radar", "civic", "tree"]; 
words.forEach((word) => {
  console.log(isPalindrome(word));
}); 
//wakka -> false
//radar -> true
//civic -> true
//tree -> false