349 lines
9 KiB
Markdown
349 lines
9 KiB
Markdown
# rehype-katex
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[![Build][build-badge]][build]
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[![Coverage][coverage-badge]][coverage]
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[![Downloads][downloads-badge]][downloads]
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[![Size][size-badge]][size]
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[![Sponsors][sponsors-badge]][collective]
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[![Backers][backers-badge]][collective]
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[![Chat][chat-badge]][chat]
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**[rehype][]** plugin to render elements with a `language-math` class with
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[KaTeX][].
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## Contents
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* [What is this?](#what-is-this)
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* [When should I use this?](#when-should-i-use-this)
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* [Install](#install)
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* [Use](#use)
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* [API](#api)
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* [`unified().use(rehypeKatex[, options])`](#unifieduserehypekatex-options)
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* [`Options`](#options)
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* [Markdown](#markdown)
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* [HTML](#html)
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* [CSS](#css)
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* [Types](#types)
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* [Compatibility](#compatibility)
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* [Security](#security)
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* [Related](#related)
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* [Contribute](#contribute)
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* [License](#license)
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## What is this?
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This package is a [unified][] ([rehype][]) plugin to render math.
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You can add classes to HTML elements, use fenced code in markdown, or combine
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with [`remark-math`][remark-math] for a `$C$` syntax extension.
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## When should I use this?
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This project is useful as it renders math with KaTeX at compile time, which
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means that there is no client side JavaScript needed.
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A different plugin, [`rehype-mathjax`][rehype-mathjax], does the same but with
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[MathJax][].
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## Install
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This package is [ESM only][esm].
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In Node.js (version 16+), install with [npm][]:
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```sh
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npm install rehype-katex
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```
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In Deno with [`esm.sh`][esmsh]:
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```js
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import rehypeKatex from 'https://esm.sh/rehype-katex@7'
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```
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In browsers with [`esm.sh`][esmsh]:
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```html
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<script type="module">
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import rehypeKatex from 'https://esm.sh/rehype-katex@7?bundle'
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</script>
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```
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## Use
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Say our document `input.html` contains:
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```html
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<p>
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Lift(<code class="language-math">L</code>) can be determined by Lift Coefficient
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(<code class="language-math">C_L</code>) like the following equation.
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</p>
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<pre><code class="language-math">
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L = \frac{1}{2} \rho v^2 S C_L
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</code></pre>
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```
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…and our module `example.js` contains:
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```js
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import rehypeDocument from 'rehype-document'
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import rehypeKatex from 'rehype-katex'
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import rehypeParse from 'rehype-parse'
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import rehypeStringify from 'rehype-stringify'
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import {read, write} from 'to-vfile'
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import {unified} from 'unified'
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const file = await unified()
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.use(rehypeParse, {fragment: true})
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.use(rehypeDocument, {
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// Get the latest one from: <https://katex.org/docs/browser>.
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css: 'https://cdn.jsdelivr.net/npm/katex@0.16.8/dist/katex.min.css'
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})
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.use(rehypeKatex)
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.use(rehypeStringify)
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.process(await read('input.html'))
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file.basename = 'output.html'
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await write(file)
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```
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…then running `node example.js` creates an `output.html` with:
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```html
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<!doctype html>
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<html lang="en">
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<head>
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<meta charset="utf-8">
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<title>input</title>
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<meta content="width=device-width, initial-scale=1" name="viewport">
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<link href="https://cdn.jsdelivr.net/npm/katex@0.16.8/dist/katex.min.css" rel="stylesheet">
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</head>
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<body>
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<p>
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Lift(<span class="katex"><!--…--></span>) can be determined by Lift Coefficient
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(<span class="katex"><!--…--></span>) like the following equation.
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</p>
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<span class="katex-display"><!--…--></span>
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</body>
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</html>
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```
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…open `output.html` in a browser to see the rendered math.
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## API
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This package exports no identifiers.
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The default export is [`rehypeKatex`][api-rehype-katex].
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### `unified().use(rehypeKatex[, options])`
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Render elements with a `language-math` (or `math-display`, `math-inline`)
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class with [KaTeX][].
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###### Parameters
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* `options` ([`Options`][api-options])
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— configuration
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###### Returns
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Transform ([`Transformer`][unified-transformer]).
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### `Options`
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Configuration (TypeScript type).
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###### Type
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```ts
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import {KatexOptions} from 'katex'
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type Options = Omit<KatexOptions, 'displayMode' | 'throwOnError'>
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```
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See [*Options* on `katex.org`][katex-options] for more info.
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## Markdown
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This plugin supports the syntax extension enabled by
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[`remark-math`][remark-math].
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It also supports math generated by using fenced code:
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````markdown
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```math
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C_L
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```
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````
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## HTML
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The content of any element with a `language-math`, `math-inline`, or
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`math-display` class is transformed.
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The elements are replaced by what KaTeX renders.
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Either a `math-display` class or using `<pre><code class="language-math">` will
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result in “display” math: math that is a centered block on its own line.
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## CSS
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The HTML produced by KaTeX requires CSS to render correctly.
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You should use `katex.css` somewhere on the page where the math is shown to
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style it properly.
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At the time of writing, the last version is:
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```html
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<!-- Get the latest one from: https://katex.org/docs/browser -->
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<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/katex@0.16.8/dist/katex.min.css">
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```
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## Types
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This package is fully typed with [TypeScript][].
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It exports the additional type [`Options`][api-options].
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## Compatibility
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Projects maintained by the unified collective are compatible with maintained
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versions of Node.js.
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When we cut a new major release, we drop support for unmaintained versions of
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Node.
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This means we try to keep the current release line, `rehype-katex@^7`,
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compatible with Node.js 16.
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This plugin works with unified version 6+ and rehype version 4+.
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## Security
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Assuming you trust KaTeX, using `rehype-katex` is safe.
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A vulnerability in it could open you to a
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[cross-site scripting (XSS)][wiki-xss] attack.
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Be wary of user input and use [`rehype-sanitize`][rehype-sanitize].
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When you don’t trust user content but do trust KaTeX, run `rehype-katex`
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*after* `rehype-sanitize`:
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```js
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import rehypeKatex from 'rehype-katex'
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import rehypeSanitize, {defaultSchema} from 'rehype-sanitize'
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import rehypeStringify from 'rehype-stringify'
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import remarkMath from 'remark-math'
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import remarkParse from 'remark-parse'
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import remarkRehype from 'remark-rehype'
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import {unified} from 'unified'
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const file = await unified()
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.use(remarkParse)
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.use(remarkMath)
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.use(remarkRehype)
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.use(rehypeSanitize, {
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...defaultSchema,
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attributes: {
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...defaultSchema.attributes,
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// The `language-*` regex is allowed by default.
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code: [['className', /^language-./, 'math-inline', 'math-display']]
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}
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})
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.use(rehypeKatex)
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.use(rehypeStringify)
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.process('$C$')
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console.log(String(file))
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```
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## Related
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* [`rehype-mathjax`][rehype-mathjax]
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— same but with MathJax
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* [`rehype-highlight`](https://github.com/rehypejs/rehype-highlight)
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— highlight code blocks
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* [`rehype-autolink-headings`](https://github.com/rehypejs/rehype-autolink-headings)
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— add links to headings
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* [`rehype-sanitize`](https://github.com/rehypejs/rehype-sanitize)
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— sanitize HTML
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* [`rehype-document`](https://github.com/rehypejs/rehype-document)
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— wrap a document around the tree
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## Contribute
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See [`contributing.md`][contributing] in [`remarkjs/.github`][health] for ways
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to get started.
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See [`support.md`][support] for ways to get help.
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This project has a [code of conduct][coc].
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By interacting with this repository, organization, or community you agree to
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abide by its terms.
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## License
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[MIT][license] © [Junyoung Choi][author]
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<!-- Definitions -->
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[build-badge]: https://github.com/remarkjs/remark-math/workflows/main/badge.svg
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[build]: https://github.com/remarkjs/remark-math/actions
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[coverage-badge]: https://img.shields.io/codecov/c/github/remarkjs/remark-math.svg
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[coverage]: https://codecov.io/github/remarkjs/remark-math
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[downloads-badge]: https://img.shields.io/npm/dm/rehype-katex.svg
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[downloads]: https://www.npmjs.com/package/rehype-katex
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[size-badge]: https://img.shields.io/bundlejs/size/rehype-katex
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[size]: https://bundlejs.com/?q=rehype-katex
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[sponsors-badge]: https://opencollective.com/unified/sponsors/badge.svg
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[backers-badge]: https://opencollective.com/unified/backers/badge.svg
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[collective]: https://opencollective.com/unified
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[chat-badge]: https://img.shields.io/badge/chat-discussions-success.svg
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[chat]: https://github.com/remarkjs/remark/discussions
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[npm]: https://docs.npmjs.com/cli/install
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[esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c
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[esmsh]: https://esm.sh
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[health]: https://github.com/remarkjs/.github
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[contributing]: https://github.com/remarkjs/.github/blob/main/contributing.md
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[support]: https://github.com/remarkjs/.github/blob/main/support.md
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[coc]: https://github.com/remarkjs/.github/blob/main/code-of-conduct.md
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[license]: https://github.com/remarkjs/remark-math/blob/main/license
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[author]: https://rokt33r.github.io
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[katex]: https://github.com/Khan/KaTeX
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[katex-options]: https://katex.org/docs/options.html
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[rehype]: https://github.com/rehypejs/rehype
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[rehype-sanitize]: https://github.com/rehypejs/rehype-sanitize
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[unified]: https://github.com/unifiedjs/unified
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[unified-transformer]: https://github.com/unifiedjs/unified#transformer
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[typescript]: https://www.typescriptlang.org
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[wiki-xss]: https://en.wikipedia.org/wiki/Cross-site_scripting
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[mathjax]: https://www.mathjax.org
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[remark-math]: ../remark-math/
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[rehype-mathjax]: ../rehype-mathjax/
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[api-options]: #options
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[api-rehype-katex]: #unifieduserehypekatex-options
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