在ES6类中声明静态常量？

问题描述

我想在类中实现常量，因为在代码中找到它们是有意义的。

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，我已经使用静态方法实现了以下解决方法：

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

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

我知道有可能为了解决原型，但是很多人都建议这样做。

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

以下是您可以做的几件事：

Here's a few things you could do:

导出 const 从模块。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;

在必要时从模块导入。或者，建立在你的静态方法的想法上，你可以声明一个 static ：

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;
  }
}

这样，你不会需要括号： / p>

That way, you won't need parenthesis:

const one = Example.constant1;

那么，正如你所说，因为一个类只是一个函数的语法糖，你可以添加一个不可写的属性，如下所示：

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

如果我们只能执行以下操作，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，这个仅在ES7提案中，甚至不允许添加 const 属性。

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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