ES6:使用命名空间导入特定值 [英] ES6: import specific values with namespace

问题描述

我不时想做一件事，我无法弄清:

There is a specific thing i want to do from time to time, that i cannot figure out:

假设module1.js导出3个值:

//module1.js

export const a = 'a';
export const b = 'b';
export const c = 'c';

然后，在module2.js中，我想将其中的两个导入到一个对象中(作为一种命名空间):

And then, in module2.js, I want to import two of these, into an object (as a kind of namespace thing):

//module2.js

import { a, c } as constants from './module1'; //<-WRONG!

所以我最终要做的是这样的:

So what I end up doing is something like this:

//module2.js

import { a, c } from './module1';
const constants = { a, c };

这可行，但是现在a和c既存在于constants中，也直接存在于模块范围中.

This works, but now a and c exist both in constants and also directly in the module scope.

有办法避免这种情况吗?

Is there a way to avoid this?

推荐答案

按照 MDN文档，您可以在整个模块内容(例如* as constants)或单个内容(例如b as constants)上设置别名.但是您不能在特定内容上设置别名.因此，解决方案之一就是使用*.

As per MDN documentation, you can either set an alias on entire module contents such as * as constants or a single content such as b as constants. But you can't set an alias on specific contents. So one of the solutions would be using *.

import * as constants from './module1';

另一种可能的解决方案是将{ a, c }作为默认值传递.

Another possible solution would be passing { a, c } as default.

//module1.js

export const a = ...
export const b = ...
export const c = ...
export const d = ...
export default { a, b, c };

/module2.js
import contants from './someModule';
doStuff(constatns);

最后，如果您不想将这些常量作为默认值传递，则可以创建一个对象并传递该对象.

Lastly, If you don't want to pass these constants as default, you can create an object and pass that object.

//module1.js

export const a = ...
export const b = ...
export const c = ...
export const b = ...
export const myCustomConstants = { a, c };

//module2.js
import { myCustomConstants } from './someModule';
doStuff(myCustomConstants);

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