Frontmatter

The comark/plugins/frontmatter plugin extracts a leading YAML frontmatter block (---) into tree.frontmatter and removes it from the markdown body before tokenization.

The plugin is enabled by default via registerDefaultPlugins. No installation or registration required.

Usage

---
title: Hello World
description: A sample document
---

# Hello World

import { parseMarkdown } from 'comark'

const result = await parseMarkdown(`---
title: Hello World
---

# Hello World
`)

console.log(result.frontmatter)
// → { title: 'Hello World' }

console.log(result.nodes)
// → [ ['h1', { id: 'hello-world' }, 'Hello World'] ]

Explicit registration

When default plugins are off, opt in with the plugin directly:

import { parseMarkdown } from 'comark'
import frontmatter from 'comark/plugins/frontmatter'

const result = await parseMarkdown(content, {
  registerDefaultPlugins: false,
  plugins: [frontmatter()],
})

Disable frontmatter parsing

Turn off all defaults (including frontmatter) so the --- block is treated as regular markdown:

const result = await parseMarkdown(content, { registerDefaultPlugins: false })
// result.frontmatter → {}

How it works

In the pre hook (before markdown-exit tokenization), the plugin:

1. Detects a leading --- … --- block via parseFrontmatter
2. Parses the YAML body into state.frontmatter
3. Strips the frontmatter from state.markdown
4. Adjusts state.parsedLines so later nodes get correct line numbers

The core parser then copies state.frontmatter onto tree.frontmatter.