vfile-matter

vfile utility to parse the YAML front matter in a file

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vfile-matter
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vfile utility parse YAML front matter.

Contents

*   [`matter(file[, options])`](#matterfile-options)
*   [`Options`](#options)
*   [`YamlOptions`](#yamloptions)

What is this?

This package parses YAML frontmatter, when found in a file, and exposes it as file.data.matter. It can optionally strip the frontmatter, which is useful for languages that do not understand frontmatter, but stripping can make it harder to deal with languages that do understand it, such as markdown, because it messes up positional info of warnings and errors.

When should I use this?

Frontmatter is a metadata format in front of content. It’s typically written in YAML and is often used with markdown. This mechanism works well when you want authors, that have some markup experience, to configure where or how the content is displayed or supply metadata about content.
When using vfiles with markdown, you are likely also using remark, in which case you should use remark-frontmatterremark-frontmatter, instead of stripping frontmatter.

Install

This package is ESM onlyesm. In Node.js (version 16+), install with npm:
npm install vfile-matter

In Deno with esm.shesmsh:
import {matter} from 'https://esm.sh/vfile-matter@5'

In browsers with esm.shesmsh:
<script type="module">
  import {matter} from 'https://esm.sh/vfile-matter@5?bundle'
</script>

Use

Say our document example.html contains:

```html

title: Hello, world!

Some more text

…and our module `example.js` looks as follows:

```js
import {read} from 'to-vfile'
import {matter} from 'vfile-matter'

const file = await read('example.html')

matter(file, {strip: true})

console.log(file.data)
console.log(String(file))

…now running node example.js yields:
{matter: {title: 'Hello, world!'}}

<p>Some more text</p>

API

This package exports the identifier matterapi-matter. There is no default export.

matter(file[, options])

Parse the YAML front matter in a file and expose it as file.data.matter.
If no matter is found in the file, nothing happens, except that file.data.matter is set to an empty object ({}).
If the file value is an Uint8Array, assumes it is encoded in UTF-8.
Parameters
— virtual file
— configuration
Returns
Nothing (undefined).

Options

Configuration (TypeScript type).
Fields
  • strip (boolean, default: false).
— remove the YAML front matter from the file
— configuration for the YAML parser, passed to [`yaml`][yaml] as `x` in
`yaml.parse('', x)`

YamlOptions

Options for the YAML parser (TypeScript type).
Equivalent to the combination of ParseOptions, DocumentOptions, SchemaOptions, and ToJsOptions.
Type
type YamlOptions = ParseOptions &
  DocumentOptions &
  SchemaOptions &
  ToJsOptions

Types

This package is fully typed with TypeScript. It exports the additional types Optionsapi-options and YamlOptionsapi-yaml-options.
To type file.data.matter, you can augment DataMap from vfile as follows:
declare module 'vfile' {
  interface DataMap {
    matter: {
      // `file.data.matter.string` is typed as `string | undefined`.
      title?: string | undefined
    }
  }
}

Compatibility

Projects maintained by the unified collective are compatible with maintained versions of Node.js.
When we cut a new major release, we drop support for unmaintained versions of Node. This means we try to keep the current release line, vfile-matter@^5, compatible with Node.js 16.

Contribute

See contributing.mdcontributing in vfile/.githubhealth for ways to get started. See support.mdsupport for ways to get help.
This project has a code of conductcoc. By interacting with this repository, organization, or community you agree to abide by its terms.

License

MITlicense © Titus Wormerauthor