在JavaScript中使用动态变量名称 [英] Use dynamic variable names in JavaScript

问题描述

在PHP中你可以做出如下惊人/可怕的事情：

In PHP you can do amazing/horrendous things like this:

$a = 1;
$b = 2;
$c = 3;
$name = 'a';
echo $$name;
// prints 1

有没有办法用Javascript做这样的事情？

Is there any way of doing something like this with Javascript?

例如如果我有 var name ='变量的名称'; 我可以获得名称 name ？

E.g. if I have a var name = 'the name of the variable'; can I get a reference to the variable with name name?

推荐答案

由于ECMA- / Javascript完全是关于对象和上下文（其中也是某些Object），每个变量都存储在一个名为变量 - 的情况下（或者在函数的情况下， 激活对象）。

Since ECMA-/Javascript is all about Objects and Contexts (which, are also somekind of Object), every variable is stored in a such called Variable- (or in case of a Function, Activation Object).

因此，如果您创建如下变量：

So if you create variables like this:

var a = 1,
    b = 2,
    c = 3;

在全局范围（= NO函数上下文）中，您隐式写那些变量进入全局对象（= 窗口在浏览器中）。

In the Global scope (= NO function context), you implicitly write those variables into the Global object (= window in a browser).

那些可以使用点或括号表示法访问：

Those can get accessed by using the "dot" or "bracket" notation:

var name = window.a;

或

var name = window['a'];

这仅适用于此特定实例中的全局对象，因为变量对象 全局对象是窗口对象本身。在函数的上下文中，您无法直接访问激活对象。例如：

This only works for the global object in this particular instance, because the Variable Object of the Global Object is the window object itself. Within the Context of a function, you don't have direct access to the Activation Object. For instance:

function foobar() {
   this.a = 1;
   this.b = 2;

   var name = window['a']; // === undefined
   alert(name);
   name = this['a']; // === 1
   alert(name);
}

new foobar();

new 创建一个新的自我实例 - 定义的对象（上下文）。如果没有 new ，该函数的范围也将是 global （= window）。此示例将分别提醒 undefined 和 1 。如果我们要替换 this.a = 1; this.b = 2 with：

new creates a new instance of a self-defined object (context). Without new the scope of the function would be also global (=window). This example would alert undefined and 1 respectively. If we would replace this.a = 1; this.b = 2 with:

var a = 1,
    b = 2;

两个警报输出都是未定义的。在这种情况下，变量 a 和 b 将从 foobar存储在激活对象中，我们无法访问（当然我们可以通过调用 a 和 b ）。

Both alert outputs would be undefined. In that scenario, the variables a and b would get stored in the Activation Object from foobar, which we cannot access (of course we could access those directly by calling a and b).

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