As @Bergi and @Mike pointed in the comments, it is up to the transpiler (most commonly Babel), how it copes with ES6 import / export. Few examples, what you'll got with Babel (with its standard plugins):
CommonJS export, ES6 import
module.exports = 1 // a.js
import one from './a' // b.js
// one === 1
module.exports = {one: 1} // a.js
import obj from './a' // b.js
// obj is {one: 1}
import * as obj from './a' // b.js
// obj.one === 1 ; however, check out the 'funky stuff' below
import {one} from './a' // b.js
// one === 1
ES6 export, CommonJS require
export default 1 // a.js
const one = require('./a').default
// one === 1
export const one = 1
const one = require('./a').one
// one === 1
Funky stuff
module.exports = 1 // a.js
import * as obj from './a' // b.js
// obj is {default: 1}
module.exports = {one: 1} // a.js
import * as obj from './a' // b.js
// obj is {one: 1, default: {one: 1}}