Pack and Unpack javascript strings

gistfile1.js

var pack = function pack (bytes) {
  var str = "";
  for(var i = 0; i < bytes.length; i += 2) {
    var char = bytes[i] << 8;
    if (bytes[i + 1])
      char |= bytes[i + 1];
    str += String.fromCharCode(char);
  }
  return str;
};

var unpack = function unpack (str) {
  var bytes = [];
  for(var i = 0; i < str.length; i++) {
    var char = str.charCodeAt(i);
    bytes.push(char >>> 8);
    bytes.push(char & 0xFF);
  }
  return bytes;
};