Javascript对象的属性已定义，但在我尝试使用它时返回undefined(Javascript object's property is defined but comes back

Javascript对象的属性已定义，但在我尝试使用它时返回undefined(Javascript object's property is defined but comes back undefined when I try to use it)

我对此完全感到困惑。 我有一个通过jquery ajax调用返回的对象。 我可以看一下对象本身，它的属性是明确定义的。 当我尝试实际访问这些属性时，它返回undefined。 例如：

console.log("data: " + data + ", data['ID']: " + data['ID']);

在控制台中打印：

data: {"ID":"2"}, data['ID']: undefined

世界上有什么可能导致这种情况？

编辑：

仅仅因为很多人问过，它对data.ID做了同样的事情。 所以这：

console.log("data: " + data + ", data.ID: " + data.ID);

打印出来：

data: {"ID":"2"}, data.ID: undefined

I am completely baffled at this. I have an object returned via a jquery ajax call. I can look at the object itself and its properties are clearly defined. When I try to actually access those properties, it comes back undefined. For example:

console.log("data: " + data + ", data['ID']: " + data['ID']);

Prints this in the console:

data: {"ID":"2"}, data['ID']: undefined

What in the world could cause this?

EDIT:

Just because a lot of people asked, it does the same thing with data.ID. So this:

console.log("data: " + data + ", data.ID: " + data.ID);

Is printing out this:

data: {"ID":"2"}, data.ID: undefined

最满意答案

如果数据是一个对象而不是你看到的[object Object]，但是你看到一个字符串，你的响应只是一个纯文本，所以你需要先解析它才能成为一个javascript对象。

使用jQuery，您可以这样做：

var dataAsObj = $.parseJSON(data)

If data would have been an object than you would have seen [object Object] but you do see a string, your response is just a plain text, so you need to parse it first to become a javascript object.

With jQuery you can do it this way:

var dataAsObj = $.parseJSON(data)