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doc: fix nits in esm.md #15315

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doc: fix nits in esm.md
vsemozhetbyt Sep 10, 2017
e9a2e0e
doc: wrap long lines in esm.md
vsemozhetbyt Sep 10, 2017
e6923cd
fixup: address a comment
vsemozhetbyt Sep 10, 2017
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37 changes: 25 additions & 12 deletions doc/api/esm.md
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Original file line number Diff line number Diff line change
Expand Up @@ -6,17 +6,21 @@
<!--name=esm-->

Node contains support for ES Modules based upon the [the Node EP for ES Modules][].
Node.js contains support for ES Modules based upon the
[Node.js EP for ES Modules][].

Not all features of the EP are complete and will be landing as both VM support and implementation is ready. Error messages are still being polished.
Not all features of the EP are complete and will be landing as both VM support
and implementation is ready. Error messages are still being polished.

## Enabling

<!-- type=misc -->

The `--experimental-modules` flag can be used to enable features for loading ESM modules.
The `--experimental-modules` flag can be used to enable features for loading
ESM modules.

Once this has been set, files ending with `.mjs` will be able to be loaded as ES Modules.
Once this has been set, files ending with `.mjs` will be able to be loaded
as ES Modules.

```sh
node --experimental-modules my-app.mjs
Expand All @@ -28,7 +32,9 @@ node --experimental-modules my-app.mjs

### Supported

Only the CLI argument for the main entry point to the program can be an entry point into an ESM graph. In the future `import()` can be used to create entry points into ESM graphs at run time.
Only the CLI argument for the main entry point to the program can be an entry
point into an ESM graph. In the future `import()` can be used to create entry
points into ESM graphs at run time.

### Unsupported

Expand All @@ -43,21 +49,26 @@ Only the CLI argument for the main entry point to the program can be an entry po

### No NODE_PATH

`NODE_PATH` is not part of resolving `import` specifiers. Please use symlinks if this behavior is desired.
`NODE_PATH` is not part of resolving `import` specifiers. Please use symlinks
if this behavior is desired.

### No `require.extensions`

`require.extensions` is not used by `import`. The expectation is that loader hooks can provide this workflow in the future.
`require.extensions` is not used by `import`. The expectation is that loader
hooks can provide this workflow in the future.

### No `require.cache`

`require.cache` is not used by `import`. It has a separate cache.

### URL based paths

ESM are resolved and cached based upon [URL](url.spec.whatwg.org) semantics. This means that files containing special characters such as `#` and `?` need to be escaped.
ESM are resolved and cached based upon [URL](https://url.spec.whatwg.org/)
semantics. This means that files containing special characters such as `#` and
`?` need to be escaped.

Modules will be loaded multiple times if the `import` specifier used to resolve them have a different query or fragment.
Modules will be loaded multiple times if the `import` specifier used to resolve
them have a different query or fragment.

```js
import './foo?query=1'; // loads ./foo with query of "?query=1"
Expand All @@ -70,9 +81,11 @@ For now, only modules using the `file:` protocol can be loaded.

All CommonJS, JSON, and C++ modules can be used with `import`.

Modules loaded this way will only be loaded once, even if their query or fragment string differs between `import` statements.
Modules loaded this way will only be loaded once, even if their query
or fragment string differs between `import` statements.

When loaded via `import` these modules will provide a single `default` export representing the value of `module.exports` at the time they finished evaluating.
When loaded via `import` these modules will provide a single `default` export
representing the value of `module.exports` at the time they finished evaluating.

```js
import fs from 'fs';
Expand All @@ -85,4 +98,4 @@ fs.readFile('./foo.txt', (err, body) => {
});
```

[the Node EP for ES Modules]: https://github.com/nodejs/node-eps/blob/master/002-es-modules.md
[Node.js EP for ES Modules]: https://github.com/nodejs/node-eps/blob/master/002-es-modules.md