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Node.js API Documentation Tooling

The Node.js API documentation is generated by an in-house tooling that resides in the nodejs/doc-kit github repository.

It is accessible in this repository from the tools/doc directory, where it is installed as an npm package.

The build process (using make doc or make doc-only) uses this tooling to parse the markdown files in doc/api/github and generate the following:

Human-readable HTML in out/doc/api/*.html
A JSON representation in out/doc/api/*.json

These artifacts are published to nodejs.org for multiple versions of Node.js. As an example the latest version of the human-readable HTML is published to nodejs.org/en/doc, and the latest version of the json documentation is published to nodejs.org/api/all.json

The artifacts are built as part of release builds by running the doc-upload github Makefile target as part of the release-sources part of the iojs+release job. This target runs the doc target to build the docs and then uses scp to copy them onto the staging/www server into a directory of the form /home/staging/nodejs/<type>/<full_version>/docs where is e.g. release, nightly, etc. The promotion step (either automatic for nightlies or manual for releases) then moves the docs to /home/dist/nodejs/docs/\<full\_version> where they are served by node.org.

The key things to know about the tooling include:

It can be invoked via executing tools/doc/node_modules/.bin/doc-kit (ex/ $ tools/doc/node_modules/.bin/doc-kit generate ...)
Its usage is detailed in the nodejs/doc-kit README github.
The tooling can process multiple files at a time.
The tooling uses a set of dependencies as described in the dependencies section.
The tooling parses the input files and does several transformations to the AST (Abstract Syntax Tree).
The tooling generates a JSON output that contains the metadata and content of the Markdown file.
The tooling generates a HTML output that contains a human-readable and ready to-view version of the file.

This documentation serves the purpose of explaining the existing tooling processes, to allow easier maintenance and evolution of the tooling. It is not meant to be a guide on how to write documentation for Node.js.

Vocabulary & Good to Know’s

AST means “Abstract Syntax Tree” and it is a data structure that represents the structure of a certain data format. In our case, the AST is a “graph” representation of the contents of the Markdown file.
MDN means Mozilla Developer Network and it is a website that contains documentation for web technologies. We use it as a reference for the structure of the documentation.
The Stability Index is used to describe the Stability of a given Node.js module. The Stability levels include:
- Stability 0: Deprecated. (This module is Deprecated)
- Stability 1: Experimental. (This module is Experimental)
- Stability 2: Stable. (This module is Stable)
- Stability 3: Legacy. (This module is Legacy)
Within Remark YAML snippets  are considered HTML nodes, that’s because YAML isn’t valid Markdown content. (Doesn’t abide by the Markdown spec)
“New Tooling” references to the (written from-scratch) API build tooling introduced in nodejs/nodejs.dev that might replace the current one from nodejs/node

Basic Tooling Usage

# cd tools/doc
npx doc-kit

# nodejs/node root directory
make doc

Writing Documentation

There should be a 1:1 relationship between module source files (lib/<module>.js) and their documentation files (doc/api/<module>.md).

The introduced_in and added YAML properties should be set to REPLACEME for new features. They will be replaced with the proper version later when it comes to releasing them.

# module

<!--introduced_in=v0.10.0-->

> Stability: 2 - Stable

A description and examples.

## `module.property`

<!-- YAML
added: v0.10.0
-->

- {type}

A description of the property.

## `module.someFunction(x, y, [z=100])`

<!-- YAML
added: v0.10.0
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/12345
    description: A description of the change.
-->

- `x` {string} The description of the string.
- `y` {boolean} Should I stay or should I go?
- `z` {number} How many zebras to bring. **Default:** `100`.

A description of the function.

\```cjs
// An example using CJS syntax.
const { someFunction } = require('module');
someFunction('a', true, 10);
\```

\```mjs
// An example using MJS syntax.
import { someFunction } from 'module';
someFunction('a', true, 10);
\```

## Event: `blerg`

<!-- YAML
added: REPLACEME
-->

- `anArg` {type} A description of the listener argument.

Modules don't usually raise events on themselves. `cluster` is the
only exception.

## Class: `SomeClass`

A description of the class.

### `SomeClass.classMethod(anArg)`

<!-- YAML
added: v0.10.0
-->

- `anArg` {Object} Just an argument.
  - `field` {string} `anArg` can have this field.
  - `field2` {boolean} Another field. **Default:** `false`.
- Returns: {boolean} `true` if it worked.

A description of the method for humans.

### `SomeClass.nextSibling()`

<!-- YAML
added: v0.10.0
-->

- Returns: {SomeClass | null} The next `SomeClass` in line.

`SomeClass` must be registered in `https://github.com/nodejs/doc-kit/blob/main/src/constants.mjs` to be properly parsed in `{type}` fields.

### `SomeClass.someProperty`

<!-- YAML
added: v0.10.0
-->

- {string}

The indication of what `someProperty` is.

### Event: `grelb`

<!-- YAML
added: v0.10.0
-->

- `isBlerg` {boolean}

This event is emitted on instances of `SomeClass`, not on the module itself.