JavaScript 復習サイト

var namae = document.cookie;
if (namae == ""){
  setName();
}
document.write(namae + "さん、ご訪問ありがとうございます。");
function setName(){
  namae = prompt("あなたの名前を入力してください","");
  if (namae == ""){
    setName();
  }
  var now = new Date();
  var yy = now.getFullYear();
  yy++;
  now.setFullYear(yy);
  var extime = now.toGMTString();
  document.cookie = namae + ";expires=" + extime;
}