使用 index.js 从“/文件夹”导入 javascript

Question

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...
}

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.

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?

Answer 1

Is this actually part of the specification?

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.

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).