在javascript对象中声明的变量范围

Question

I was trying to understand the scope of variables in javascript objects. 我试图了解javascript对象中变量的范围。 But the behavior that I am getting seems to be a little off the road. 但我得到的行为似乎有点不起作用。 To put it simply, if I have an object that defines a function as a variable, then the function variable is not able to access other variables of the object in which it is defines. 简单地说，如果我有一个将函数定义为变量的对象，那么函数变量就无法访问其定义的对象的其他变量。 The code below will make things clear. 下面的代码将使事情变得清晰。

<html>
<head>
    <script type="text/javascript">

        var someObject = {
            someVariable : 5,
            getVariable: function() {
                return someVariable;
            }
        };

        window.onload = function () {
            alert(someObject.getVariable());
        };

    </script>
</head>
<body>
    Hello There
</body>
</html>

The above code gives "ReferenceError: someVariable is not defined" for the someVariable in function getVariable(). 上面的代码为函数getVariable（）中的someVariable提供了“ReferenceError：someVariable is not defined” 。 Would anyone like to comment on this behavior? 有人想评论这种行为吗？

Answer 1

Absolutely. 绝对。

The "variable" you're talking about isn't a "variable", it's a property of an object (the object happening to be a variable). 你所谈论的“变量”不是一个“变量”，它是一个对象的property （该对象恰好是一个变量）。

As such, you have two options. 因此，您有两种选择。
Assuming that your object is made like this: 假设您的对象是这样的：

var obj = {
    property : 42,
    everything : function () { /* ... */ }
};

The two options for inside of your function body, to return the value 42 are: 函数体内部的两个选项，返回值42是：

obj.property;

OR 要么

this.property;

When you call: 你打电话时：

obj.everything();

The JS interpreter will see obj as being equal to this inside of the function. 该JS解释器将看到obj为等于this函数的内部。
Or you reference obj itself, directly, and access property using either .property dot-notation, or ["property"] bracket-notation. 或者直接引用obj本身，并使用.property dot-notation或["property"]括号表示法访问property 。

Answer 2

That is not a variable, that is a property/field of an object. 这不是变量，即对象的属性/字段。

Try this.someVariable . 试试this.someVariable 。

Here this is a (rather special) variable that points to the object, and the dot (or square bracket) syntax can be used to access fields of that object. this是一个指向对象的（相当特殊的）变量，点（或方括号）语法可用于访问该对象的字段。

You can also do someObject.someVariable in places where someObject (another variable pointing at the object) is in scope. 您还可以在someObject （指向对象的另一个变量）在范围内的位置执行someObject.someVariable 。

Answer 3

Try this.someVariable : 试试this.someVariable ：

var someObject = {
        someVariable: 5,
        getVariable: function () {
            return this.someVariable;
        }
    };

window.onload = function () {
    alert(someObject.getVariable());
};

在javascript对象中声明的变量范围

问题描述

3 个解决方案

解决方案1
3 2012-11-06 01:27:00

解决方案2
1 2012-11-06 01:23:35

解决方案3
0 2012-11-06 01:22:57

在javascript对象中声明的变量范围

问题描述

3 个解决方案

解决方案1 3 2012-11-06 01:27:00

解决方案2 1 2012-11-06 01:23:35

解决方案3 0 2012-11-06 01:22:57

解决方案1
3 2012-11-06 01:27:00

解决方案2
1 2012-11-06 01:23:35

解决方案3
0 2012-11-06 01:22:57