循环通过JSON数组给出“未定义”结果[重复]

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I have a JSON String being parsed (in a response var) from AJAX:

我从AJAX中解析了一个JSON字符串（在响应变量中）：

The JSON

JSON

{
   "TheArray":[  
      {  
         "AlmostThere": {  
            "whatWeAreLookingFor":"Hello"
         }
      },
      {
        "AlmostThere": {
            "whatWeAreLookingFor":"Goodbye"
        }
      }
   ]
}

The JSON being parsed

正在解析的JSON

var jsonData = JSON.parse(response); //response is the string version of the JSON code!

Now, I need to loop into the JSON array, hereby mentioned as TheArray. I do this:

现在，我需要循环到JSON数组，特此提到为TheArray。我这样做：

Looping TheArray

循环TheArray

for (var contents in jsonData["TheArray"]) {

}

And inside there, we get the value of the whatWeAreLookingFor element:

在那里，我们得到了whatWeAreLookingFor元素的值：

for (var contents in jsonData["TheArray"]) {
    console.log(contents.whatWeAreLookingFor + "!");
}

But there is a catch! The console outputs... undefined!. - I have tried multiple ways to make this work, such as using contents["whatWeAreLookingFor"] and what-not, but I still get the same results.

但是有一个问题！控制台输出......未定义！ - 我已经尝试了多种方法来完成这项工作，例如使用内容[“whatWeAreLookingFor”]和什么不是，但我仍然得到相同的结果。

3 个解决方案

#1

You forgot to access AlmostThere

你忘了访问AlmostThere

  jsonData.TheArray[i].AlmostThere.whatWeAreLookingFor

for (var i = 0; i < jsonData.TheArray.length; i++) {
    console.log(jsonData.TheArray[i].AlmostThere.whatWeAreLookingFor);
}

#2

If you loop your array TheArray in your way, the contents var will become these two objects:

如果以你的方式循环你的数组TheArray，内容var将成为这两个对象：

{  
     "AlmostThere": {  
        "whatWeAreLookingFor":"Hello"
     }
}

and

和

{
    "AlmostThere": {
        "whatWeAreLookingFor":"Goodbye"
    }
}

Now you want to access the value with

现在您想要访问该值

contents.whatWeAreLookingFor

contents.whatWeAreLookingFor

but this attribute is undefined for these objects. So your console logs undefined. You have to access the value with that:

但是对于这些对象，此属性未定义。所以你的控制台记录未定义。您必须使用以下内容访问该值：

contents.AlmostThere.whatWeAreLookingFor

So you get the object AlmostThere and select the attribute whatWeAreLookingFor.

因此，您获取对象AlmostThere并选择属性whatWeAreLookingFor。

If your using jquery you should use:

如果你使用jquery你应该使用：

$.each(jsonData.TheArray, function() {
     console.log(contents.AlmostThere.whatWeAreLookingFor + '!');
});

API: http://api.jquery.com/jquery.each/

API：http：//api.jquery.com/jquery.each/

#3

for... in iterates over the keys of an object. For an array, that means (approximately) the indexes 0, 1, 2, etc.

for ... in迭代对象的键。对于数组，这意味着（大约）索引0,1,2等。

You could use Array.prototype.forEach instead:

您可以使用Array.prototype.forEach代替：

jsonData.theArray.forEach(function(contents) {
  console.log(contents.AlmostThere.whatWerAreLookingFor);
})

#1