How can I use an ES6 import in Node js

Question

I m trying to get the hang of ES6 imports in Node js and am trying to use the syntax provided in this example  Cheatsheet Link I m looking through the support table  but I was not able to find what version supports the new import statements  I tried looking for the text import require   I m currently running Node js 8 1 2 and also believe that since the cheatsheet is referring to  js files it should work with  js files  As I run the code  taken from the cheatsheet s first example   import   square  diag   from  lib    I get the error   SyntaxError  Unexpected token import   Reference to library I m trying to import    ------ lib js ------ export const sqrt   Math sqrt  export function square x        return x   x    export function diag x  y        return sqrt square x    square y       What am I missing and how can I get node to recognize my import statement

User · Answer

Using the  mjs extension  as suggested in the accepted answer  in order to enable ECMAScript modules works  However  with Node js v12  you can also enable this feature globally in your package json file  The official documentation states   import statements of  js and extensionless files are treated as ES modules if the nearest parent package json contains  quot type quot    quot module quot         quot type quot    quot module quot      quot main quot    quot   src index js quot      Of course you still have to provide the flag --experimental-modules when starting your application

User · Answer

You can also use npm package called esm which allows you to use ES6 modules in Node js  It needs no configuration  With esm you will be able to use export import in your JavaScript files  Run the following command on your terminal yarn add esm  or npm install esm  After that  you need to require this package when starting your server with node  For example if your node server runs index js file  you would use the command node -r esm index js  You can also add it in your package json file like this      quot name quot    quot My-app quot      quot version quot    quot 1 0 0 quot      quot description quot    quot Some Hack quot      quot main quot    quot index js quot      quot scripts quot          quot test quot    quot echo   quot Error  no test specified  quot   amp  amp  exit 1 quot        quot start quot    quot node -r esm index js quot           Then run this command from the terminal to start your node server npm start  Check this link for more details

User · Answer

If you are using the modules system on the server side  you do not need to use Babel at all  To use modules in Node js ensure that   Use a version of node that supports the --experimental-modules flag Your   js files must then be renamed to   mjs  That s it  However and this is a big however  while your shinny pure ES6 code will run in an environment like Node js  e g   9 5 0  you will still have the craziness of transpilling just to test  Also bear in mind that Ecma has stated that release cycles for JavaScript are going to be faster  with newer features delivered on a more regular basis  Whilst this will be no problems for single environments like Node js  it s a slightly different proposition for browser environments  What is clear is that testing frameworks have a lot to do in catching up  You will still need to probably transpile for testing frameworks  I d suggest using Jest  Also be aware of bundling frameworks  You will be running into problems there

User · Answer

I don t know if this will work for your case  but I am running an Express js server with this  nodemon --inspect   index js --exec babel-node --presets es2015 stage-2  This gives me the ability to import and use spread operator even though I m only using Node js version 8  You ll need to install babel-cli  babel-preset-es2015  and babel-preset-stage-2 to do what I m doing

User · Answer

I just wanted to use the import and export in JavaScript files  Everyone says it s not possible  But  as of May 2018  it s possible to use above in plain Node js  without any modules like Babel  etc  Here is a simple way to do it  Create the below files  run  and see the output for yourself  Also don t forget to see Explanation below  File myfile mjs function myFunc         console log  quot Hello from myFunc quot      export default myFunc   File index mjs import myFunc from  quot   myfile mjs quot      Simply using  quot   myfile quot  may not work in all resolvers  myFunc     Run node  --experimental-modules  index mjs  Output  node 12020  ExperimentalWarning  The ESM module loader is experimental   Hello from myFunc  Explanation   Since it is experimental modules   js files are named  mjs files While running you will add --experimental-modules to the node index mjs While running with experimental modules in the output you will see   quot  node 12020  ExperimentalWarning  The ESM module loader is experimental   quot  I have the current release of Node js  so if I run node --version  it gives me  quot v10 3 0 quot   though the LTE stable recommended version is 8 11 2 LTS  Someday in the future  you could use  js instead of  mjs  as the features become stable instead of Experimental  More on experimental features  see  https   nodejs org api esm html

User · Answer

Node js has included experimental support for ES6 support  Read more about here  https   nodejs org docs latest-v13 x api esm html esm enabling   TLDR  Node js  gt   v13 It s very simple in Node js 13 and above  You need to either   Save the file with  mjs extension  or Add    quot type quot    quot module quot    in the nearest package json   You only need to do one of the above to be able to use ECMAScript modules  Node js  lt   v12 If you are using Node js version 8-12  save the file with ES6 modules with  mjs extension and run it like  node --experimental-modules my-app mjs

User · Answer

You may try esm  Here is some introduction  esm

User · Answer

Back to Jonathan002 s original question about           what version supports the new ES6 import statements     based on the article by Dr  Axel Rauschmayer  there is a plan to have it supported by default  without the experimental command line flag  in Node js 10 x LTS   According to node js s release plan as it is on 3 29  2018  it s likely to become available after Apr 2018  while LTS of it will begin on October 2018

User · Answer

Using Node js v12 2 0  I can import all standard modules like this  import   as Http from  http  import   as Fs from  fs  import   as Path from  path  import   as Readline from  readline  import   as Os from  os   Versus what I did before  const   Http   require  http      Fs   require  fs      Path   require  path      Readline   require  readline      Os   require  os    Any module that is an ECMAScript module can be imported without having to use an  mjs extension as long as it has this field in its package json file   quot type quot    quot module quot   So make sure you put such a package json file in the same folder as the module you re making  And to import modules not updated with ECMAScript module support  you can do like this     Implement the old require function import   createRequire   from  module  const require   createRequire import meta url      Now you can require whatever const   WebSocket   require  ws      Mime   require  mime-types      Chokidar   require  chokidar    And of course  do not forget that this is needed to actually run a script using module imports  not needed after v13 2   node --experimental-modules my-script-that-use-import js  And that the parent folder needs this package json file for that script to not complain about the import syntax       quot type quot    quot module quot     If the module you want to use has not been updated to support being imported using the import syntax then you have no other choice than using require  but with my solution above that is not a problem   I also want to share this piece of code which implements the missing   filename and   dirname constants in modules  import  fileURLToPath  from  url  import  dirname  from  path  const   filename   fileURLToPath import meta url  const   dirname   dirname   filename

User · Answer

Use     quot devDependencies quot          quot  babel core quot    quot  7 2 0 quot        quot  babel preset-env quot    quot  7 2 0 quot        quot  babel register quot    quot  7 0 0 quot       File  babelrc      quot presets quot     quot  babel preset-env quot      Entry point for the Node js application  require  quot  babel register quot           Import the rest of our application  module exports   require    index js    See How To Enable ES6 Imports in Node js

User · Answer

Solution https   www npmjs com package babel-register    This is to allow ES6 export syntax    to be properly read and processed by node js application require  babel-register       presets         env                After that  any line you add below that has typical ES6 export syntax    will work just fine  const utils   require        utils js    const availableMixins   require           src lib mixins index js     Below is definition of file  mixins index js export   default as FormValidationMixin   from    form-validation      eslint-disable-line import prefer-default-export  That worked just fine inside my Node js CLI application

[node.js] How can I use an ES6 import in Node.js?

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