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Vivliostyle Flavored Markdown

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Vivliostyle Flavored Markdown (VFM), a Markdown syntax optimized for book authoring. It is standardized and published for Vivliostyle and its sibling projects.

Table of contents

Install

npm install -g @vivliostyle/vfm

Use

vfm --help
vfm README.md
echo "# Hello" | vfm

Usage with vivliostyle command

npm i -g @vivliostyle/cli
vfm README.md --style https://raw.githubusercontent.com/jagat-xpub/cosmology/gh-pages/css/scholarly.css > book.html
vivliostyle build book.html -s A4

API

npm install --save @vivliostyle/vfm
# or
yarn add @vivliostyle/vfm
import { stringify } from '@vivliostyle/vfm';

console.log(
  stringify(`
# はじめに

{Vivliostyle|ビブリオスタイル}の世界へようこそ。
`),
);

This snippet will generates:

<!doctype html>
<html>
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <title>はじめに</title>
  </head>
  <body>
    <h1>はじめに</h1>
    <p>
      <ruby>Vivliostyle<rt>ビブリオスタイル</rt></ruby
      >の世界へようこそ。
    </p>
  </body>
</html>

Options

style (default: undefined)

Set the specified value as the href attribute of <link rel="stylesheet">.

stringify('# Hello', { style: 'https://example.com/book.css' });

will generates:

<!doctype html>
<html>
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <link rel="stylesheet" href="https://example.com/book.css" />
  </head>
  <body>
    <p><h1>Hello</h1></p>
  </body>
</html>

style can be an array of styles.

stringify('# Hello', {
  style: ['https://example.com/book.css', 'https://example.com/extra.css'],
});

will generates:

<!doctype html>
<html>
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <link rel="stylesheet" href="https://example.com/book.css" />
    <link rel="stylesheet" href="https://example.com/extra.css" />
  </head>
  <body>
    <p><h1>Hello</h1></p>
  </body>
</html>

partial (default: false)

If true is specified, only the HTML defined in <body> is output.

stringify('# Hello', { partial: true });

will generates:

<p><h1>Hello</h1></p>

title (default: undefined)

Set the specified value as the text of <title>.

stringify('# Hello', { title: 'Hello' });

will generates:

<!doctype html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>Hello</title>
    <meta name="viewport" content="width=device-width, initial-scale=1" />
  </head>
  <body>
    <p><h1>Hello</h1></p>
  </body>
</html>

language (default: undefined)

Set the specified value as the lang attribute of <html>.

stringify('# Hello', { language: 'ja' });

will generates:

<!doctype html>
<html lang="ja">
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
  </head>
  <body>
    <p><h1>Hello</h1></p>
  </body>
</html>

hardLineBreaks (default: false)

Converts line breaks to <br>.

stringify(
  `
new
line
`,
  { hardLineBreaks: true },
);

will generates:

<!doctype html>
<html>
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
  </head>
  <body>
    <p>
      new<br />
      line
    </p>
  </body>
</html>

disableFormatHtml (default: false)

Disable automatic HTML format. Explicitly specify true if want unformatted HTML during development or debug.

stringify(
  `text`,
  { disableFormatHtml: true },
);

will generates:

<!doctype html>
<html>
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
</head>
<body>
<p>text</p>
</body>
</html>

math (default: true)

Handles math syntax. The default value is true, which is valid.

stringify(
  `$x = y$`
);

will generates:

<!doctype html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <script async src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.9/MathJax.js?config=TeX-MML-AM_CHTML"></script>
  </head>
  <body data-math-typeset="true">
    <p><span class="math inline">\(x = y\)</span></p>
  </body>
</html>

To explicitly disable it, specify false for this option or math: false for Markdown's Frontmatter.

stringify(
  `$x = y$`,
  { math: false }
);

will generates:

<!doctype html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
  </head>
  <body>
    <p>$x = y$</p>
  </body>
</html>

Advanced usage

Unified processor

import { VFM } from '@vivliostyle/vfm';

const processor = VFM({ partial: true });
const html = processor.processSync('# Hello').toString();

Unified plugin

import unified from 'unified';
import vfm from '@vivliostyle/vfm/lib/revive-parse';
import html from '@vivliostyle/vfm/lib/revive-rehype';

function main() {
  unified()
    .use(vfm)
    .use(customRemarkPlugin)
    .use(html)
    .use(customRehypePlugin)
    .processSync('# Hello');
}

readMetadata

Read metadata from Markdown frontmatter.

Useful if just want to get the metadata, Markdown parse and metadata typing (for TypeScript) are handled by the VFM side.

readMetadata(md: string, customKeys: string[]): Metadata

  • params:
    • md: String Markdown text.
    • customKeys: String[] A collection of key names to be ignored by meta processing.
  • returns:
    • metadata: Metadata Metadata.
import { readMetadata } from '@vivliostyle/vfm'

const md = `---
id: 'my-page'
lang: 'en'
dir: 'ltr'
class: 'my-class'
title: 'Title'
vfm:
  math: false
  theme: 'sample.css'
---
`;

const metadata = readMetadata(md);
console.log(metadata);

About Metadata details, refer to VFM's "Frontmatter" or type information of TypeScript.

About customKeys

Use this if want to add custom metadata with a third party tool.

Keys that are not defined as VFM are treated as meta. If you specify a key name in customKeys, the key and its data type will be preserved and stored in custom instead of meta.

import { readMetadata } from '@vivliostyle/vfm'

const md = `---
title: 'Title'
tags: ['foo', 'bar']
---
`;

const metadata = readMetadata(md, ['tags']);
console.log(metadata);

Results:

{
  title: 'title',
  custom: {
    tags: ['foo', 'bar']
  }
}

tags is stored and retained structure in custom instead of meta.

If specify a default key such as title, it will be processed as custom.

User-specified metadata

Metadata can be specified for stringify, this specification takes precedence over Frontmatter.

The following usage is assumed.

  • Use metadata other than Frontmatter
  • Process Frontmatter metadata obtained by readMetadata
stringify(
  '# Title',
  {},
  { title: 'My Page', body: [{ name: 'id', value: 'page' }] },
);

HTML:

<!doctype html>
<html>
  <head>
    <meta charset="utf-8">
    <title>My Page</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
  </head>
  <body id="page">
    <section id="title" class="level1">
      <h1>Title</h1>
    </section>
  </body>
</html>

Spec

Current Status

Principles

  1. Open: steadily improving through open discussion and feedback from the vast community.
  2. Consistent: Provides reference implementation for parsing and converting VFM to HTML, allowing other non Vivliostyle projects to use this syntax for their purposes.

Links

Contribution

We want you to:

Maintainers