esm

The brilliantly simple, babel-less, bundle-less ECMAScript module loader.

> esm is the world’s most advanced ECMAScript module loader.
This fast, production ready, zero dependency loader is all you need to support
ECMAScript modules in Node 6+. See the release post
and video for details!

Install
---

* __New projects__

Run npm init esm or yarn create esm.

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

* __Existing projects__

Run npm i esm or yarn add esm.

Getting started
---

There are two ways to enable esm.

1. Enable esm for packages:

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

__index.js__
``js
// Set options as a parameter, environment variable, or rc file.
require = require("esm")(module/, options/)
module.exports = require("./main.js")
`
__main.js__
`js
// ESM syntax is supported.
export {}
`
:bulb: These files are automagically created with npm init esm or yarn create esm.

2. Enable esm for local runs:

`shell
node -r esm main.js
`
:bulb: Omit the filename to enable esm in the REPL.

Features
---

:clap: By default, :100: percent CJS interoperability is enabled so you can get stuff done.

:lock: .mjs files are limited to basic functionality without support for esm options.

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

* Passing all applicable test262 compliance tests
* import/export
* import.meta
* Dynamic import
* Live bindings
* File URI scheme
* Node stdin, --eval, --print flags
* Node --check flag _(Node 10+)_

Options
---

Specify options with one of the following:

* "esm" field in package.json
* CJS/ESM in an .esmrc.js, .esmrc.cjs, or .esmrc.mjs file
* JSON6 in an .esmrc or .esmrc.json file
* JSON6 or file path in the ESM_OPTIONS environment variable
* ESM_DISABLE_CACHE environment variable

DevOpts
---

Tips
---

$3

* For bundlers like browserify+esmify,
parcel-bundler, and webpack
add a "module" field to package.json pointing to the main ES module.
`json
"main": "index.js",
"module": "main.js"
`

:bulb: This is automagically done with npm init esm or yarn create esm.

$3

* Enable esm for wallaby.js following their
integration example.

$3

* Load esm before loaders/monitors like
@babel/register,
newrelic,
sqreen, and
ts-node.

* Load esm for jasmine using the
"helpers"
field in jasmine.json:
`json
"helpers": [
"node_modules/esm"
]
`

* Load esm with “node-args" options of:

- pm2: --node-args="-r esm"

* Load esm with “require” options of
ava,
mocha,
nodemon,
nyc,
qunit,
tape, and
webpack.

:bulb: Builtin require cannot sideload .mjs files. However, .js files
can be sideloaded or .mjs files may be loaded with dynamic import`.