Javascript全局变量存储在哪个对象中？ [英] What object are Javascript global variables stored in?

问题描述

全局变量是否存储在特定的对象中？例如：

  var test =stuff; 
 console.log（window.test）; 
 console.log（document.test）; 
 console.log（this.test）; 
  

所有这三个测试的结果都是 undefined ，那么是否有一个对象持有这些变量？

我感觉好像这是愚蠢的，我应该已经知道，但我似乎甚至不能找到在线回答。

解决方案

我想你会发现在大多数浏览器中， code> window 。

疯狂的心理调试尝试：你在jsFiddle中测试了这个吗？或者在Firebug中？如果是这样，你可能会看到 undefined ，因为在这种情况下代码是在一个框架中执行的;所以它有一个不同的窗口对象（我认为）代码实际上是包装的：

<$ p $ （）;
console.log（window.test）;
console。 window.addEvent（'load'，function（）{
var test =stuff;
console.log log（document.test）;
console.log（this.test）;
}）;


您可以从上面的jsFiddle代码片段中看到 test 不是全局变量，这解释了为什么它没有附加到窗口。

我不是专家，但从Chrome，Firefox，Safari和Opera中可以看出，这个答案看起来是准确的。为了验证，我创建了一个包含以下内容的HTML文件，并将其加载到每个浏览器中：

 < script type =text / JavaScript的> 
 var test =stuff; 
 alert（window.test）; 
< / script> 
  

果然，每次都是东西。

Are global variables stored in specific object? For instance:

var test="stuff";
console.log(window.test);
console.log(document.test);
console.log(this.test);

All three of these tests result in undefined, so is there an object that holds these variables?

I feel as though this is something stupid that I should already know, but I can't even seem to find the answer online.

解决方案

I think you'll find on most browsers, they are stored in window.

Far-fetched psychic debugging attempt: did you test this in jsFiddle? Or perhaps in Firebug? If so, you're probably seeing undefined for all three because in that case the code is executed in a frame; so it has a different window object (I think) the code is actually wrapped:

window.addEvent('load', function() {
  var test="stuff";
  console.log(window.test);
  console.log(document.test);
  console.log(this.test);
});

You can see from the above snippet from jsFiddle that test is not a global variable, which explains why it hasn't been attached to window.

I'm no expert, but this answer appears to be accurate from what I can tell in Chrome, Firefox, Safari, and Opera. To verify, I created an HTML file with the following content and loaded it in each browser:

<script type="text/javascript">
  var test = "stuff";
  alert(window.test);
</script>

Sure enough, "stuff" every time.

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