text: function AddressBook() {
  	this.contacts = [];
  	this.initialComplete = false;
  }
  //编写getInitialContacts函数并使其带有异步特征
  AddressBook.prototype.getInitialContacts = function(cb) {
  	var self =this;
  	//使用setTimeout来做使其带有异步特征
  	setTimeout(function() {
  		//这是函数运行结束后要做的事情
  		self.initialComplete = true;
  		if(cb) {
  			return cb();
  		}
  	}, 3);
  }
  
  AddressBook.prototype.addContact = function(contact) {
  	this.contacts.push(contact);
  }
  
  AddressBook.prototype.getContact = function(index) {
  	return this.contacts[index];
  }
  
  AddressBook.prototype.deleteContact = function(index) {
  	//使用splice方法来删除数组
  	this.contacts.splice(index, 1);
  }