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ES2018 examples using ESM

This is a minimal example about the different usages of ESM and how it compares to using node directly It shows how easy it is to use ESM with no additional configuration (webpack, babel, rollup, etc.) which is just perfect when you want to get things done fast without spending/wasting time configuring all the boilerplate for ES2018 or import/export features!

Basically, this is a showcase of the 2 different usages of ESM

  • through custom require (main file loader), see ./esm-loader.js
  • through node -r esm script.js which requires esm before requiring the script.js, and therefore support import/export in node 6+

Note that special stuff like spread operator do require node v8.6.0+, support of such features (ES2018) is not provided by ESM

Testing it out yourself!

  • yarn run node will load index.js using node and fail due to lack of support of node in any existing version (node 6 to 11)
yarn run v1.13.0
$ node ./index.js
/Users/vadorequest/dev/es2018-esm-examples/index.js:1
(function (exports, require, module, __filename, __dirname) { import map from 'lodash.map'; // import/export won't work with standard node not loaded through ESM
                                                              ^^^^^^

SyntaxError: Unexpected token import
    at createScript (vm.js:80:10)
    at Object.runInThisContext (vm.js:139:10)
    at Module._compile (module.js:616:28)
    at Object.Module._extensions..js (module.js:663:10)
    at Module.load (module.js:565:32)
    at tryModuleLoad (module.js:505:12)
    at Function.Module._load (module.js:497:3)
    at Function.Module.runMain (module.js:693:10)
    at startup (bootstrap_node.js:188:16)
    at bootstrap_node.js:609:3
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
  • yarn run esm-loader will load index.js through esm-loader.js and fail if node version is <8.6.0, but will work if higher version of node is used
yarn run v1.13.0
$ node esm-loader.js
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{ '0': 4, '1': 5, '2': 6 }
✨  Done in 0.22s.
  • yarn run node-with-esm will load index.js using node with esm compatible mode and fail if node version is <8.6.0, but will work if higher version of node is used
yarn run v1.13.0
$ node -r esm ./index.js
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{ '0': 4, '1': 5, '2': 6 }
✨  Done in 0.22s.
  • yarn run node-with-esm:watch will load index.js using nodemon with esm compatible mode and fail if node version is <8.6.0, but will work if higher version of node is used
yarn run v1.13.0
$ nodemon -r esm ./index.js
[nodemon] 1.18.10
[nodemon] to restart at any time, enter `rs`
[nodemon] watching: *.*
[nodemon] starting `node -r esm ./index.js`
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{ '0': 4, '1': 5, '2': 6 }
[nodemon] clean exit - waiting for changes before restart

Nodemon is great for scripting/prototyping hence the fact it's in the showcase :)

See package.json:scripts.