是否可以访问函数的闭包？ [英] Is it possible to gain access to the closure of a function?

问题描述

JavaScript中的函数通过保留（隐藏）链接到其封闭范围来形成闭包。

A function in javascript forms a closure by keeping a (hidden) link to its enclosing scope.

当我们有函数（作为变量值）时，是否可以以编程方式访问它？

Is it possible to access it programmatically when we have the function (as a variable value) ?

真正的目标是理论上的，但演示可以列出闭包的属性。

The real goal is theoretical but a demonstration could be to list the properties of the closure.

var x = (function(){
   var y = 5;
   return function() {
       alert(y);
   };
})();

//access y here with x somehow

推荐答案

这是（一个）闭包的目的 - 保持信息私有。由于函数已经被执行，其范围变量不再可以从外部使用（并且从未被使用过） - 只有在其范围内（仍然）执行的函数才能访问。

That's (one of) the purpose(s) of a closure - to keep information private. Since the function already has been executed its scope variables are no longer available from outside (and have never been) - only the functions executed in it's scope (still) have access.

但是，您可以通过getters / setters授予访问权限。

However you could give access via getters/setters.

您可能需要查看 Stuart Langridge的谈话关于闭包。非常值得推荐的还有Douglas Crockfords的解释。你可以使用闭包做很多奇特的事情;）

You might want to take a look into Stuart Langridge's talk about closures. Very recommendable are also Douglas Crockfords Explanations. You can do lots of fancy stuff with closures;)

编辑：
你有几个选项来检查闭包：在webdeveloper控制台中观察对象，或者我经常这样做）返回一个调试函数，它将所有的私有变量转储到控制台。

You have several options to examine the closure: Watch the object in the webdeveloper console or (as I do it often) return a debug-function which dumps out all the private variables to the console.

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