使用 index.js 从“/文件夹"导入 javascript [英] javascript import from '/folder' with index.js

问题描述

我注意到了一些类似以下内容的案例:

I've noticed a few cases where I've seen something like the following:

// /reducers/reducer1.js
export default function reducer1(state = {}, action){
  // etc...
}
  
// /reducers/reducer2.js
export default function reducer2(state = {}, action){
  // etc...
}

// /reducers/index.js
import { combineReducers } from 'redux';
import reducer1 from './reducer1';
import reducer2 from './reducer2';

export default combineReducers({
  reducer1,
  reducer2
})
  
// /store.js
import masterReducer from './reducers';

export default function makeStore(){
  // etc...
}

注意最后一个文件"我们调用 import masterReducer from './reducers' - 有些人似乎认为这应该从 index.js 文件中导入 default export.

Notice the last "file" where we call import masterReducer from './reducers' - A few people seem to believe this should import the default export from the index.js file.

这实际上是规范的一部分吗?- 我的解释/问题是，这是许多人使用 WebPack v1 的结果，该版本将 import 语句转换为 CommonJS 样式的 requires 语句?或者这是否会在 WebPack v2 中使用官方"中断?import/export 支持吗?

Is this actually part of the specification? - my interpretation/question is that this is the result of many folks using WebPack v1 which translates import statements into CommonJS-style requires statements? Or will this break in WebPack v2 with "official" import/export support?

推荐答案

这实际上是规范的一部分吗?

Is this actually part of the specification?

没有.模块标识符('./reducers' 在您的情况下)如何解析为实际模块由模块加载器/捆绑器的实现决定，ES6 没有具体说明.而且它似乎也没有在 CommonJs 中指定.

No. How module identifiers ('./reducers' in your case) are resolved to the actual modules is left to the implementation of the module loader/bundler, it's not specificed by ES6. And it doesn't seem to be specified in CommonJs either.

这就是 node 的工作方式 - 当需要一个目录时，将使用 index.js 文件.像 browserify 或 webpack 遵循这个约定(出于兼容性原因).

This is just how node does it - when requiring a directory, it's index.js file will be used. Bundlers like browserify or webpack followed this convention (for compat reasons).

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