ES6: "import * as alias" vs "import alias"

Question

Is there any difference between:

import utils from 'utils'

and

import * as utils from 'utils'?

In case A:

//utils.js export function doSomething() { //... } 

In case B:

//utils.js export function doSomething() { //... } export default function doSomethingDefault() { //... } 

UPDATE:

I was mislead by intellisense feature of vscode, but as recommended a small test on node+babel showed the difference:

//index.js import utilsCaseA from './utils1' import * as utilsCaseAWildcard from './utils1' var utilsCaseARequire = require('./utils1')  import utilsCaseB from './utils2' import * as utilsCaseBWildcard from './utils2' var utilsCaseBRequire = require('./utils2')  var compareObjects =  {     utilsCaseA, utilsCaseAWildcard, utilsCaseARequire,utilsCaseB,utilsCaseBWildcard,utilsCaseBRequire }; console.log(compareObjects); 

Answer 1

From your example:

Case A:

//utils.js export function doSomething() { //... } 

Case B:

//utils.js export function doSomething() { //... } export default function doSomethingDefault() { //... } 

Result:

import utils from 'utils' utils() // (Case A: undefined, Case B: doSomethingDefault)  import * as utils from 'utils' utils // (Case A: utils = { doSomething: function }, Case B: utils = { doSomething: function, default: function })  import { doSomething } from 'utils' doSomething() // (both Case A and Case B: doSomething = doSomething) 

The difference between Case A and Case B is that, in Case A import utils from 'utils', utils will be undefined because there is no default export. In case B, utils will refer to doSomethingDefault.

With import * as utils from 'utils', in Case A utils will have one method (doSomething), while in Case B utils will have two methods (doSomething and default).