Javascript：通过名称访问闭包中的局部变量或变量 [英] Javascript: Get access to local variable or variable in closure by its name

问题描述

可能重复：

大家好。

我们都知道，你可以使用[]语法访问javascript对象的属性。例如ob ['nameOfProperty']。

Hi all.
We all know that you can access a property of a javascript object by it's name using the [] syntax.. e.g. ob['nameOfProperty'].

你能为局部变量做同样的事吗？另一个回答这里建议的答案是使用window [' nameOfVar']。但是，这只适用于海报，因为他正在窗口级范围定义变量。

Can you do the same for a local variable? Another answer here suggested the answer is to use window['nameOfVar']. However, this only worked for the poster as he was defining variables at window-level scope.

我假设这一定是可能的，因为Firefox的Firebug相信是用javascript写的）可以显示局部变量和闭包变量。有没有一些隐藏的语言功能，我不知道？

I assume that this must be possible in general, as Firefox's Firebug (which I believe is written in javascript) can show local and closure variables. Is there some hidden language feature I'm not aware of?

具体来说，这里是我想做的：

Specifically, here's what I want to do:

 var i = 4;
 console.log(window['i']); // this works..

 function Func(){
     var j = 99;

     // try to output the value of j from its name as a string
     console.log(window['j']); // unsurprisingly, this doesn't work
 }

 Func();

推荐答案

引用局部变量类似（虽然可能应考虑所有变量内部引用字符串）。

I'm not aware of anything built into JavaScript to reference local variables like that (though there probably should be considering all variables are internally referenced by strings).

我建议保持所有的变量在一个对象，如果你真的需要通过字符串访问：

I'd suggest keeping all your variables in an object if you really need to access by string:

var variables = {
    "j": 1
};
alert(variables["j"]);

更新：这种错误我没有办法像你想要的那样。内部变量是声明环境记录中的可变绑定。属性绑定到对象，它们是通过对象的环境记录的属性，但实际上有一种方法使用括号访问它们。不幸的是，没有办法以同样的方式访问声明式环境记录。

Update: It kind of bugs me that there's no way to do this like you want. Internally the variable is a mutable binding in the declarative environment records. Properties are bound to the object they're a property of through the object's environment records, but there's actually a way to access them using brackets. Unfortunately, there's no way to access the declarative environment records the same way.

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