ES6 Destructuring and Module imports

问题

I was under the impression that this syntax:

import Router from 'react-router';
var {Link} = Router;

has the same final result as this:

import {Link} from 'react-router';

Can someone explain what the difference is?

(I originally thought it was a React Router Bug.)

回答1:

import {Link} from 'react-router';

imports a named export from react-router, i.e. something like

export const Link = 42;

import Router from 'react-router';
const {Link} = Router;

pulls out the property Link from the default export, assuming it is an object, e.g.

export default {
  Link: 42
};

(the default export is actually nothing but a standardized named export with the name "default").

See also export on MDN.

Complete example:

// react-router.js
export const Link = 42;
export default {
  Link: 21,
};


// something.js
import {Link} from './react-router';
import Router from './react-router';
const {Link: Link2} = Router;

console.log(Link); // 42
console.log(Link2); // 21

With Babel 5 and below I believe they have been interchangeable because of the way ES6 modules have been transpiled to CommonJS. But those are two different constructs as far as the language goes.

回答2:

To do this:

import {purple, grey} from 'themeColors';

Without repeating export const for each symbol, just do:

export const
  purple = '#BADA55',
  grey = '#l0l',
  gray = grey,
  default = 'this line actually causes an error';

来源：https://stackoverflow.com/questions/33524696/es6-destructuring-and-module-imports

标签

javascript

ecmascript-6

destructuring

es6-modules