嵌套ES6类？ [英] Nested ES6 classes?

问题描述

似乎可以在一个构造函数中嵌套一个类，然后可以从类中的任何位置实例化，这个官方是否可以？

It seems possible to nest a class in a constructor which can then be instantiated from anywhere within the class, is this official?

例如， p>

E.g.,

class C {

    constructor() {
        class D {
            constructor() { }
        }
    }

    method() {
        var a = new D();  // works fine
    }

}

//var a = new D();  // fails in outer scope

traceur生成的JS https://google.github.io/traceur-compiler/demo/repl.html

The traceur generated JS https://google.github.io/traceur-compiler/demo/repl.html

$traceurRuntime.ModuleStore.getAnonymousModule(function() {
  "use strict";
  var C = function C() {
    var D = function D() {};
    ($traceurRuntime.createClass)(D, {}, {});
  };
  ($traceurRuntime.createClass)(C, {method: function() {
      var a = new D();
    }}, {});
  return {};
});
//# sourceURL=traceured.js

推荐答案

不，ES6中没有嵌套的类，如果你的意思是这样的话，那么在类语法中就没有这样的私人成员了。

No, there are no nested classes in ES6, and there is no such thing as private members in the class syntax anyway if you mean that.

当然可以把第二类作为另一个类的静态属性，如下所示：

Of course you can put a second class as a static property on another class, like this:

class A {
    …
}
A.B = class {
    …
};

或您使用额外的范围：

var C;
{
    class D {
        constructor() { }
    }
    C = class C {
        constructor() { }
        method() {
            var a = new D();  // works fine
        }
    }
}

^{（似乎有一个bug跟踪，因为它使用一个悬挂的 var 作为类声明而不是块范围）}

^{(There seems to be a bug with traceur as it uses a hoisted var for the class declaration instead of block scope)}

使用提出的类字段语法，也可以编写单个表达式或声明：

With the proposed class field syntax, it will also be possible to write a single expression or declaration:

class A {
    …
    static B = class {
         …
    }
};

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