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micromark-extension-frontmatter
Advanced tools
micromark extension to support frontmatter (YAML, TOML, etc)
The micromark-extension-frontmatter package is an extension for micromark, a Markdown parser, that allows for the parsing of frontmatter. Frontmatter is metadata at the beginning of a Markdown file, typically used for configuration or data storage purposes.
Parsing YAML Frontmatter
This feature allows you to parse YAML frontmatter in a Markdown file. The code sample demonstrates how to use the micromark-extension-frontmatter to parse a Markdown string containing YAML frontmatter and convert it to HTML.
const micromark = require('micromark');
const { frontmatter } = require('micromark-extension-frontmatter');
const markdown = `---
title: Example Title
author: John Doe
---
# Hello World
`;
const html = micromark(markdown, {
extensions: [frontmatter()]
});
console.log(html);
Parsing TOML Frontmatter
This feature allows you to parse TOML frontmatter in a Markdown file. The code sample demonstrates how to use the micromark-extension-frontmatter to parse a Markdown string containing TOML frontmatter and convert it to HTML.
const micromark = require('micromark');
const { frontmatter } = require('micromark-extension-frontmatter');
const markdown = `+++
title = "Example Title"
author = "John Doe"
+++
# Hello World
`;
const html = micromark(markdown, {
extensions: [frontmatter('toml')]
});
console.log(html);
Parsing JSON Frontmatter
This feature allows you to parse JSON frontmatter in a Markdown file. The code sample demonstrates how to use the micromark-extension-frontmatter to parse a Markdown string containing JSON frontmatter and convert it to HTML.
const micromark = require('micromark');
const { frontmatter } = require('micromark-extension-frontmatter');
const markdown = `{
"title": "Example Title",
"author": "John Doe"
}
# Hello World
`;
const html = micromark(markdown, {
extensions: [frontmatter('json')]
});
console.log(html);
gray-matter is a popular package for parsing frontmatter from strings or files. It supports YAML, JSON, and TOML frontmatter. Unlike micromark-extension-frontmatter, which is an extension for micromark, gray-matter is a standalone package that can be used independently of any Markdown parser.
front-matter is another package for parsing frontmatter from strings. It supports YAML frontmatter and is simpler and more lightweight compared to gray-matter. It does not support TOML or JSON frontmatter, making it less versatile than micromark-extension-frontmatter.
markdown-it-front-matter is a plugin for the markdown-it Markdown parser that allows for the extraction of frontmatter. It primarily supports YAML frontmatter. This package is similar to micromark-extension-frontmatter in that it is an extension for a specific Markdown parser.
micromark extension to support frontmatter (YAML, TOML, etc).
This package contains extensions that add support for frontmatter.
As there is no spec for frontmatter in markdown, this extension follows how YAML frontmatter works on github.com. For the HTML part, instead of rendering YAML, it is ignored. Other types of frontmatter can be parsed, which will by default also work the same as on github.com.
These tools are all low-level.
In many cases, you want to use remark-frontmatter
with remark
instead.
When you do want to use micromark
, you can use this.
When working with mdast-util-from-markdown
, you must combine this package
with mdast-util-frontmatter
.
This package is ESM only. In Node.js (version 12.20+, 14.14+, 16.0+, or 18.0+), install with npm:
npm install micromark-extension-frontmatter
In Deno with esm.sh
:
import {frontmatter, frontmatterHtml} from 'https://esm.sh/micromark-extension-frontmatter@1'
In browsers with esm.sh
:
<script type="module">
import {frontmatter, frontmatterHtml} from 'https://esm.sh/micromark-extension-frontmatter@1?bundle'
</script>
import {micromark} from 'micromark'
import {frontmatter, frontmatterHtml} from 'micromark-extension-frontmatter'
const output = micromark('---\na: b\n---\n# c', {
extensions: [frontmatter()],
htmlExtensions: [frontmatterHtml()]
})
console.log(output)
Yields:
<h1>c</h1>
This package exports the identifiers frontmatter
and frontmatterHtml
.
There is no default export.
The export map supports the endorsed development
condition.
Run node --conditions development module.js
to get instrumented dev code.
Without this condition, production code is loaded.
frontmatter(options?)
Add support for parsing frontmatter in markdown.
Function that can be called to get a syntax extension for micromark (passed
in extensions
).
Supports YAML by default. Can be configured to support TOML and more.
options
Configuration (optional).
One preset
or Matter
, or an array of them, defining all
the supported frontmatters (default: 'yaml'
).
preset
Either 'yaml'
or 'toml'
:
'yaml'
— Matter
defined as {type: 'yaml', marker: '-'}
'toml'
— Matter
defined as {type: 'toml', marker: '+'}
Matter
An object with a type
and either a marker
or a fence
:
type
(string
)
— type to tokenize asmarker
(string
or {open: string, close: string}
)
— character used to construct fences.
By providing an object with open
and close
different characters can be
used for opening and closing fences.
For example the character '-'
will result in '---'
being used as the
fencefence
(string
or {open: string, close: string}
)
— string used as the complete fence.
By providing an object with open
and close
different values can be used
for opening and closing fences.
This can be used too if fences contain different characters or lengths other
than 3anywhere
(boolean
, default: false
)
– if true
, matter can be found anywhere in the document.
If false
(default), only matter at the start of the document is recognizedfrontmatterHtml(options?)
Add support for turning frontmatter in markdown to HTML.
Function that can be called to get an HTML extension for micromark (passed
in htmlExtensions
).
This makes sure nothing is generated for frontmatter.
Supports YAML by default. Can be configured to support other things.
See options
above for more info.
Here are a couple of example of different matter objects and what frontmatter they match.
To match frontmatter with the same opening and closing fence, namely three of
the same markers, use for example {type: 'yaml', marker: '-'}
, which matches:
---
key: value
---
To match frontmatter with different opening and closing fences, which each use
three different markers, use for example
{type: 'custom', marker: {open: '<', close: '>'}}
, which matches:
<<<
data
>>>
To match frontmatter with the same opening and closing fences, which both use
the same custom string, use for example {type: 'custom', fence: '+=+=+=+'}
,
which matches:
+=+=+=+
data
+=+=+=+
To match frontmatter with different opening and closing fences, which each use
different custom strings, use for example
{type: 'json', fence: {open: '{', close: '}'}}
, which matches:
{
"key": "value"
}
When authoring markdown with frontmatter, it’s recommended to use YAML frontmatter if possible. While YAML has some warts, it works in the most places, so using it guarantees the highest chance of portability.
In certain ecosystems, other flavors are widely used. For example, in the Rust ecosystem, TOML is often used. In such cases, using TOML is an okay choice.
When possible, do not use other types of frontmatter, and do not allow frontmatter anywhere.
Frontmatter does not relate to HTML elements. It is typically stripped, which is what this plugin does.
This package does not relate to CSS.
Frontmatter forms with, roughly, the following BNF:
; Note: `fence` is an arbitrary, configured, fence.
frontmatter ::= fence *space_or_tab eol *( *code eol ) fence *space_or_tab
This package is fully typed with TypeScript.
It exports the additional type Options
.
This package is at least compatible with all maintained versions of Node.js. As of now, that is Node.js 12.20+, 14.14+, 16.0+, and 18.0+. It also works in Deno and modern browsers.
This package is safe.
remarkjs/remark-frontmatter
— remark plugin using this to support frontmattersyntax-tree/mdast-util-frontmatter
— mdast utility to support frontmatterSee contributing.md
in micromark/.github
for ways to get
started.
See support.md
for ways to get help.
This project has a code of conduct. By interacting with this repository, organization, or community you agree to abide by its terms.
FAQs
micromark extension to support frontmatter (YAML, TOML, etc)
The npm package micromark-extension-frontmatter receives a total of 897,660 weekly downloads. As such, micromark-extension-frontmatter popularity was classified as popular.
We found that micromark-extension-frontmatter demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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