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A fast, production ready, zero-dependency ES module loader for Node 6+!

See the releasepostandvideo for all the details.

• New projects

  Runnpm init esm oryarn create esm.

  💡 Use the-y flag to answer “yes” to all prompts.

• Existing projects

  Runnpm i esm oryarn add esm.

There are two ways to enableesm.

1. Enableesm for packages:

   Useesm to load the main ES module and export it as CommonJS.

   index.js

   // Set options as a parameter, environment variable, or rc file.require=require("esm")(module/*, options*/)module.exports=require("./main.js")

   main.js

   // ESM syntax is supported.export{}

   💡 These files are automagically created withnpm init esm oryarn create esm.

2. Enableesm for local runs:

   node -r esm main.js

   💡 Omit the filename to enableesm in the REPL.

Theesm loader bridges the ESM oftoday to theESM oftomorrow.

👏 By default, 💯 percent CJS interoperability is enabled so you can get stuff done fast.
🔒.mjs files are limited to basic functionality without support foresm options.

Out of the boxesm just works, no configuration necessary, and supports:

• Passing all applicabletest262 compliance tests
• import/export
• import.meta
• Dynamicimport
• Live bindings
• File URI scheme
• Nodestdin,--eval,--print flags
• Node--check flag(Node 10+)

Specify options with one of the following:

• "esm" field inpackage.json
• CJS/ESM in an.esmrc.js or.esmrc.mjs file
• JSON6 in an.esmrc or.esmrc.json file
• JSON6 or file path in theESM_OPTIONS environment variable
• ESM_DISABLE_CACHE environment variable

• For bundlers likebrowserify+esmify,parcel-bundler, andwebpackadd a"module" field topackage.json pointing to the main ES module.

  "main":"index.js","module":"main.js"

  💡 This is automagically done withnpm init esm oryarn create esm.

• Enable ESM syntax forwallaby.js following theirintegration example.

• Loadesm before loaders/monitors like@babel/register,newrelic,sqreen, andts-node.

• Loadesm forjasmine using the"helpers"field injasmine.json:

  "helpers": ["node_modules/esm"]

• Loadesm with “node-args" options of:
  

  • node-tap:--node-arg=-r --node-arg=esm
  • pm2:--node-args="-r esm"

• Loadesm with “require” options ofava,mocha,nodemon,nyc,qunit,tape, andwebpack.

  💡 Builtinrequire cannot sideload.mjs files. However,.js filescan be sideloaded or.mjs files may be loaded with dynamicimport.