在 ES6 类中声明静态常量? [英] Declaring static constants in ES6 classes?

问题描述

我想在 class 中实现常量，因为在代码中定位它们是有意义的.

I want to implement constants in a class, because that's where it makes sense to locate them in the code.

到目前为止，我一直在使用静态方法实现以下解决方法:

So far, I have been implementing the following workaround with static methods:

class MyClass {
    static constant1() { return 33; }
    static constant2() { return 2; }
    // ...
}

我知道有可能摆弄原型，但许多人建议不要这样做.

I know there is a possibility to fiddle with prototypes, but many recommend against this.

有没有更好的方法在 ES6 类中实现常量?

Is there a better way to implement constants in ES6 classes?

推荐答案

您可以执行以下操作:

从模块导出一个const.根据您的用例，您可以:

Export a const from the module. Depending on your use case, you could just:

export const constant1 = 33;

并在必要时从模块导入.或者，基于您的静态方法想法，您可以声明一个 static 获取访问器:

And import that from the module where necessary. Or, building on your static method idea, you could declare a static get accessor:

const constant1 = 33,
      constant2 = 2;
class Example {

  static get constant1() {
    return constant1;
  }

  static get constant2() {
    return constant2;
  }
}

那样，你就不需要括号了:

That way, you won't need parenthesis:

const one = Example.constant1;

Babel REPL 示例

然后，正如你所说，由于 class 只是一个函数的语法糖，你可以像这样添加一个不可写的属性:

Then, as you say, since a class is just syntactic sugar for a function you can just add a non-writable property like so:

class Example {
}
Object.defineProperty(Example, 'constant1', {
    value: 33,
    writable : false,
    enumerable : true,
    configurable : false
});
Example.constant1; // 33
Example.constant1 = 15; // TypeError

如果我们能做这样的事情可能会很好:

It may be nice if we could just do something like:

class Example {
    static const constant1 = 33;
}

但不幸的是，这个类属性语法仅在 ES7 提案中，即使如此它不允许将 const 添加到属性中.

But unfortunately this class property syntax is only in an ES7 proposal, and even then it won't allow for adding const to the property.

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