permutations code found on the internet for bonfire challenge

gistfile1.txt

function permAlone(str) {
 
  var permArr = [], usedChars = [];
  function permute(input) {
  //convert input into a char array (one element for each character)
    var i, ch, chars = input.split("");
    for (i = 0; i < chars.length; i++) {
    //get and remove character at index "i" from char array
      ch = chars.splice(i, 1);
    //add removed character to the end of used characters
      usedChars.push(ch);
    //when there are no more characters left in char array to add, add used chars to list of permutations
      if (chars.length == 0) permArr[permArr.length] = usedChars.join("");
    //send characters (minus the removed one from above) from char array to be permuted
      permute(chars.join(""));
    //add removed character back into char array in original position
      chars.splice(i, 0, ch);
    //remove the last character used off the end of used characters array
      usedChars.pop();
  }
    return permArr;
}
  permArr = permute(str);
  
  // filter out duplicates from permArr
  
  permArr = permArr.filter(function(perm, index) {
    perm = perm.split('');
    return perm.every(function(letter, index) {
      if (index === perm.length-1) {
        return true;
      }
      return (letter !== perm[index+1]);
    });
  });
  
  
  return permArr.length;
}

permAlone('baa');