convert arraybuffer to string and string to arraybuffer

ab2str.js

function ab2str(buf) {
  return String.fromCharCode.apply(null, new Uint8Array(buf));
}

str2ab.js

function str2ab(str) {
  var buf = new ArrayBuffer(str.length*2); // 2 bytes for each char
  var bufView = new Uint8Array(buf);
  for (var i=0, strLen=str.length; i < strLen; i++) {
    bufView[i] = str.charCodeAt(i);
  }
  return buf;
}