Question

我在这里问了一个问题： Extending javascript literal object

因为我忘了回来而被解决了。现在我没有忘记返回，我再次未定义，为什么？

<script>
    var secretAgent = (function(){
      var person = {},
          firstName = "James",
          lastName = "Bond";
      person.WhoAreYou = function() {
        alert("My name is " + this.lastName + ", " + this.firstName + " " + this.lastName);
      };
      return person;
    })();
  </script>

  <script>
    secretAgent.WhoAreYou();
  </script>

更新：为什么我的工作不起作用，而我认为我的工作与下面的工作方式相同：

http://enterprisejquery.com/2010/10/how-good-c-habits-can-encourage-bad-javascript-habits-part-1/

//Revealing Module Pattern (Public & Private)
var skillet = (function() {
    var pub = {},
        //Private property
        amountOfGrease = "1 Cup";

    //Public property   
    pub.ingredient = "Bacon Strips";

    //Public method
    pub.fry = function() {
        console.log( "Frying " + pub.ingredient );
    };

    //Private method
    function privateWay() {
        //Do something...
    }

    //Return just the public parts
    return pub;
}());

//Public Properties
console.log( skillet.ingredient ); //Bacon Strips

//Public Methods
skillet.fry();

//Adding a public property to a Module
skillet.quantity = 12;
console.log( skillet.quantity ); //12

//Adding a public method to a Module
skillet.toString = function() {
    console.log( skillet.quantity + " " +
                 skillet.ingredient + " & " +
                 amountOfGrease + " of Grease" );
};

try {
    //Would have been successful,
    //but can't access private variable
    skillet.toString();
} catch( e ) {
    console.log( e.message ); //amountOfGrease is not defined
}

Answer 1

您需要在文字本身声明这些属性（而不是分离不相关的变量），如下所示：

var secretAgent = (function(){
  var person = { firstName: "James", lastName: "Bond" };
  person.WhoAreYou = function() {
    alert("My name is " + this.lastName + ", " + this.firstName + " " + this.lastName);
  };
  return person;
})();

You can test it out here

Answer 2

我看到这里有两个问题。

你再次忘记了回归。 :-) WhoAreYou函数实际上没有返回任何内容，只是提醒。因此secretAgent.WhoAreYou()也返回undefined。
警报显示“我的名字未定义，未定义未定义”。这是因为所使用的变量的范围。您将WhoAreYou分配到person，并在正文中引用this.lastName。这里的this是指person变量，正如您所看到的，此对象没有lastName属性。

有两种方法可以解决后一个问题。首先，通过将名称变量添加到person对象：

var secretAgent = (function(){
  var person = {};
  person.firstName = "James";
  person.lastName = "Bond";
  person.WhoAreYou = function() {
    alert("My name is " + this.lastName + ", " + this.firstName + " " + this.lastName);
  };
  return person;
}    
)();

// Although the first three lines would be more natural as:
var person = { firstname: "James", lastName: "Bond" };

其次，您可以选择删除this引用，它将引用您刚刚定义的局部变量：

var secretAgent = (function(){
  var person = {},
  firstName = "James",
  lastName = "Bond";
  person.WhoAreYou = function() {
    alert("My name is " + lastName + ", " + firstName + " " + lastName);
  };
  return person;
}    
)();

在两个示例中，您当然需要向returns函数添加适当的WhoAreYou。

Answer 3

从变量中删除“this”，因为你在匿名函数中将它们设置为var，使用这个指向该函数，而不是你现在调用它们的“Person”。

<script>
  var secretAgent = (function(){
    var person = {},
    firstName = "James",
    lastName = "Bond";
    person.WhoAreYou = function() {
      alert("My name is " + lastName + ", " + firstName + " " + lastName);
    };
    return person;
  }    
  )();
</script>

<script>
  secretAgent.WhoAreYou();
</script>

示例：JSFiddle

Answer 4

为什么不呢：

var secretAgent = {
    firstName: "James",
    lastName: "Bond",
    whoAreYou: function() {
        alert("My name is " + this.lastName + ", " + 
              this.firstName + " " + this.lastName);
    }
};

Answer 5

您定义firstName和lastName的方式不是对象person本身的字段。但是它们是WhoAreYou功能的上限值。所以你可以写这样的函数：

person.WhoAreYou = function() {
    alert("My name is " + this.lastName + ", " + this.firstName + " " + this.lastName);
};

就像那些是函数的私有变量一样。另一种方法是将filelds声明为对象本身，如下所示：

var person = {
    firstName: "James",
    lastName: "Bond",
};

这个方法可以像你写的一样工作。

Answer 6

变量this在您的情况下为person，同时firstName和lastName被定义为局部变量，但不是person的属性，所以你可以通过名字在匿名函数中访问它们：

var secretAgent = (function(){
  var person = {},
      firstName = "James",
      lastName = "Bond";
  person.WhoAreYou = function() {
    alert("My name is " + lastName + ", " + firstName + " " +lastName);
  };
  return person;
})();
secretAgent.WhoAreYou();

匿名函数和未定义成员值的问题

6 个答案: