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    This package has been deprecated

    Author message:

    This package is discontinued. Use


    0.26.0 • Public • Published


    This fast, small, zero-dependency package is all you need to enable ES modules in Node 6+ today!

    See the release post 📖 and video 🎥 for all the details.


    This package has been discontinued in favor of esm.

    Getting started

    Run npm i --save @std/esm in your app or package directory.

    There are three ways to enable ESM with @std/esm.

    1. Enable ESM with a CJS bridge:


      // Provide options as a parameter, environment variable, or rc file.
      require = require("@std/esm")(module/*, options*/)
      module.exports = require("./main.mjs").default
    2. Enable ESM in the Node CLI with the -r option:

      node -r @std/esm main.mjs
    3. Enable ESM in the Node REPL:

      node -r @std/esm

      or upon entering:

      $ node
      > require("@std/esm")
      @std/esm enabled

    Note: All "cjs" options are unlocked in the Node REPL.

    Standard Features

    The @std/esm loader is as spec-compliant as possible and follows Node’s ESM rules.

    👉 This means, by default, ESM requires the use of the .mjs file extension.
    🔓 You can unlock ESM with the .js file extension using the "js" ESM mode.

    Out of the box @std/esm just works, no configuration necessary, and supports:


    Unlock features with options specified as one of the following:

    • The "@std/esm" field in your package.json
    • JSON6 in an .esmrc or .esmrc.json file
    • JSON6 or file path in the ESM_OPTIONS environment variable
    • CJS/ESM in an .esmrc.js or .esmrc.mjs file

    Commonly used options may be specified in shorthand form:

    • "@std/esm":"js" is shorthand for "@std/esm":{"mode":"js"}
    • "@std/esm":"cjs" is shorthand for "@std/esm":{"cjs":true,"mode":"js"}

    A string mode:

    • "all" files as ESM
    • "js" and other files with import, import.meta, export, or "use module" as ESM

    A boolean or object to unlock CJS features in ESM.

    Unlockable Features

    A boolean for storing ES modules in require.cache.


    A boolean for respecting require.extensions in ESM.


    A boolean for __esModule interoperability.


    A boolean for importing named exports of CJS modules.


    A boolean for following CJS path rules in ESM.


    A boolean for top-level return.


    A boolean for __dirname, __filename, and require in ESM.



    A boolean for top-level await in modules without ESM exports. (requires Node 7.6+)




    A boolean for toggling cache creation or string path of the cache directory.


    A boolean for unmasking stack traces.


    A boolean for including inline source maps.


    A boolean for logging development parse and runtime warnings.



    • Load @std/esm before @babel/register v7+
    • Load @std/esm with the “require” option of ava, mocha, nyc, and tape
    • Load @std/esm with the --node-arg=-r --node-arg=@std/esm option of node-tap
    • Load @std/esm with the --node-args="-r @std/esm" option of pm2
    • Load @std/esm with wallaby.js
    • Use @std/esm to load jasmine
    • Use "@std/esm":"cjs" for the --watch and --watch-extensions options of mocha
    • Use "@std/esm":"cjs" for ava and webpack
    • When in doubt, use "@std/esm":"cjs"


    npm i @std/esm

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    • jdalton