javascript - 在JavaScript中使用动态变量名称(Use dynamic variable names in JavaScript)

Question

In PHP you can do amazing/horrendous things like this:(在PHP中，您可以执行以下令人惊奇/可怕的事情：)

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

Is there any way of doing something like this with Javascript?(有没有办法用Java做类似的事情？)

Eg if I have a var name = 'the name of the variable';(例如，如果我有一个var name = 'the name of the variable';)

can I get a reference to the variable with name name ?(如何获得名称为name的变量的引用？)   ask by Finbarr translate from so

Answer 1

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 ).(由于ECMA // Javascript都是关于Objects和Contexts （它们也是某种对象）的，因此每个变量都存储在所谓的Variable- （如果是Function，则为Activation Object ）中。)

So if you create variables like this:(因此，如果您创建这样的变量：)

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

In the Global scope (= NO function context), you implicitly write those variables into the Global object (= window in a browser).(在全局范围 （= NO函数上下文）中，您将这些变量隐式写入全局对象 （=浏览器中的window ）。)

Those can get accessed by using the "dot" or "bracket" notation:(可以使用“点”或“括号”表示法来访问它们：)

var name = window.a;

or(要么)

var name = window['a'];

This only works for the global object in this particular instance, because the Variable Object of the Global Object is the window object itself.(这仅在此特定实例中适用于全局对象，因为全局对象的变量 对象是window对象本身。)

Within the Context of a function, you don't have direct access to the Activation Object .(在函数的上下文中，您没有直接访问Activation Object的权限。) For instance:(例如：)

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

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

new foobar();

new creates a new instance of a self-defined object (context).(new创建一个自定义对象（上下文）的新实例。)

Without new the scope of the function would be also global (=window).(没有new功能，该功能的范围也将是global （=窗口）。) This example would alert undefined and 1 respectively.(此示例将分别警告undefined和1 。) If we would replace this.a = 1; this.b = 2(如果我们将其替换this.a = 1; this.b = 2) this.a = 1; this.b = 2 with:(this.a = 1; this.b = 2其中：)

var a = 1,
    b = 2;

Both alert outputs would be undefined.(两个警报输出均未定义。)

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 ).(在这种情况下，变量a和b将存储在foobar的激活对象中，我们无法访问它（当然，我们可以通过调用a和b直接访问它们）。)