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readme.md

rehype-mathjax

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rehype plugin to render elements with a language-math class with MathJax.

Contents

What is this?

This package is a unified (rehype) plugin to render math. You can add classes to HTML elements, use fenced code in markdown, or combine with remark-math for a $C$ syntax extension.

When should I use this?

This project is useful as it renders math with MathJax at compile time, which means that there is no client side JavaScript needed.

A different plugin, rehype-katex, does the same but with KaTeX.

Install

This package is ESM only. In Node.js (version 18+), install with npm:

npm install rehype-mathjax

In Deno with esm.sh:

import rehypeMathjax from 'https://esm.sh/rehype-mathjax@6'

In browsers with esm.sh:

<script type="module">
  import rehypeMathjax from 'https://esm.sh/rehype-mathjax@6?bundle'
</script>

Use

Say our document input.html contains:

<p>
  Lift(<code class="language-math">L</code>) can be determined by Lift Coefficient
  (<code class="language-math">C_L</code>) like the following equation.
</p>
<pre><code class="language-math">
  L = \frac{1}{2} \rho v^2 S C_L
</code></pre>

…and our module example.js contains:

import rehypeMathjax from 'rehype-mathjax'
import rehypeParse from 'rehype-parse'
import rehypeStringify from 'rehype-stringify'
import {read, write} from 'to-vfile'
import {unified} from 'unified'

const file = await unified()
  .use(rehypeParse, {fragment: true})
  .use(rehypeMathjax)
  .use(rehypeStringify)
  .process(await read('input.html'))

file.basename = 'output.html'
await write(file)

…then running node example.js creates an output.html with:

<p>
  Lift(<mjx-container class="MathJax" jax="SVG"><!--…--></mjx-container>) can be determined by Lift Coefficient
  (<mjx-container class="MathJax" jax="SVG"><!--…--></mjx-container>) like the following equation.
</p>
<mjx-container class="MathJax" jax="SVG" display="true"><!--…--></mjx-container>
<style>
mjx-container[jax="SVG"] {
  direction: ltr;
}
/* … */
</style>

…open output.html in a browser to see the rendered math.

API

This package has an export map with several entries for plugins using different strategies:

  • rehype-mathjax/browser — browser (±1kb)
  • rehype-mathjax/chtml — CHTML (±154kb)
  • rehype-mathjax/svg — SVG (±566kb)
  • rehype-mathjax — same as SVG

Each module exports the plugin rehypeMathjax as the default export.

unified().use(rehypeMathjax[, options])

Render elements with a language-math (or math-display, math-inline) class with MathJax.

Parameters
  • options (Options, typically optional) — configuration
Returns

Transform (Transformer).

Options

Configuration (TypeScript type).

Fields
Notes

When using rehype-mathjax/browser, only options.tex.displayMath and options.tex.inlineMath are used. That plugin will use the first delimiter pair in those fields to wrap math. Then you need to load MathJax yourself on the client and start it with the same markers. You can pass other options on the client.

When using rehype-mathjax/chtml, options.chtml.fontURL is required. For example:

  // …
  .use(rehypeMathjaxChtml, {
    chtml: {
      fontURL: 'https://cdn.jsdelivr.net/npm/mathjax@3/es5/output/chtml/fonts/woff-v2'
    }
  })
  // …

Markdown

This plugin supports the syntax extension enabled by remark-math. It also supports math generated by using fenced code:

```math
C_L
```

HTML

The content of any element with a language-math, math-inline, or math-display class is transformed. The elements are replaced by what MathJax renders. Either a math-display class or using <pre><code class="language-math"> will result in “display” math: math that is a centered block on its own line.

CSS

The HTML produced by MathJax does not require any extra CSS to render correctly.

Types

This package is fully typed with TypeScript. It exports the additional type Options.

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, rehype-mathjax@^6, compatible with Node.js 18.

This plugin works with unified version 6+ and rehype version 4+.

Security

Assuming you trust MathJax, using rehype-mathjax is safe. A vulnerability in it could open you to a cross-site scripting (XSS) attack. Be wary of user input and use rehype-sanitize.

When you don’t trust user content but do trust MathJax, run rehype-mathjax after rehype-sanitize:

import rehypeMathjax from 'rehype-mathjax'
import rehypeSanitize, {defaultSchema} from 'rehype-sanitize'
import rehypeStringify from 'rehype-stringify'
import remarkMath from 'remark-math'
import remarkParse from 'remark-parse'
import remarkRehype from 'remark-rehype'
import {unified} from 'unified'

const file = await unified()
  .use(remarkParse)
  .use(remarkMath)
  .use(remarkRehype)
  .use(rehypeSanitize, {
    ...defaultSchema,
    attributes: {
      ...defaultSchema.attributes,
      // The `language-*` regex is allowed by default.
      code: [['className', /^language-./, 'math-inline', 'math-display']]
    }
  })
  .use(rehypeMathjax)
  .use(rehypeStringify)
  .process('$C$')

console.log(String(file))

Related

Contribute

See contributing.md in remarkjs/.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.

License

MIT © TANIGUCHI Masaya