/*字典 Dictionary類*/function Dictionary() {  this.add = add;  this.datastore = new Array();  this.find = find;  this.remove = remove;  this.showAll = showAll;  this.count = count;  this.clear = clear;}function add(key, value) {  this.datastore[key] = value;}function find(key) {  return this.datastore[key];}function remove(key) {  delete this.datastore[key];}function showAll() {  var str = "";  for(var key in this.datastore) {    str += key + " -> " + this.datastore[key] + "; "  }  console.log(str);}function count() {  /*var ss = Object.keys(this.datastore).length;  console.log("ssss  "+ss);  return Object.keys(this.datastore).length;*/  /**/  var n = 0;  for(var key in Object.keys(this.datastore)) {    ++n;  }  console.log(n);  return n;}function clear() {  for(var key in this.datastore) {    delete this.datastore[key];  }}var pbook = new Dictionary();pbook.add("Mike", "723");pbook.add("Jennifer", "987");pbook.add("Jonathan", "666");pbook.showAll();//Mike -> 723; Jennifer -> 987; Jonathan -> 666;pbook.count();//3pbook.remove("Jennifer");//pbook.clear();pbook.showAll();//Mike -> 723; Jonathan -> 666;pbook.count();//2