rehype-katex-browser

v1.0.0

Published

3 months ago

rehype plugin to transform inline and block math with KaTeX (only renders in browser)

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swwind233

unified remark rehype rehype-plugin plugin mdast markdown hast html math katex latex tex

`rehype-katex-browser`

Sometimes I think it's stupid to compile katex in MDX on the server, which generates thousands of lines of js code and makes your bundle larger than using katex in the browser itself.

If you have the same problem, I recommend you to switch to this module and just replace rehype-katex with rehype-katex-browser. Also remark-math is still required.

And also provide a katex component for MDX as it will generate following code.

$$
E = mc^2
$$

$\log{a^b} = b \log{a}$

<pre>
  <code className="language-math math-display">
    <katex mode="display" content="E = mc^2" />
  </code>
</pre>

<code className="language-math math-inline">
  <katex mode="inline" content="\log{a^b} = b \log{a}">
</code>

Write your own <katex /> component and provide it via @mdx-js/react, @mdx-js/preact or using <MDXContent components={{ katex: Katex }} /> yourself.

If you are really lazy, you can use this code directly.

import { useEffect, useRef } from "preact/hooks";
import katex from "katex";

import "katex/dist/katex.css"; // or other ways

type Props = {
  mode: "inline" | "display";
  content: string;
};

export function Katex(props: Props) {
  const ref = useRef<HTMLSpanElement>(null);

  useEffect(() => {
    katex.render(props.content, ref.current!, {
      displayMode: props.mode === "display",
      throwOnError: false,
    });
  }, [props.mode, props.content]);

  return <span ref={ref} />;
}

rehype-katex

$Build$ $Coverage$

rehype plugin to render <span class=math-inline> and <div class=math-display> with KaTeX.

What is this?

This package is a unified (rehype) plugin to render math. You can combine it with remark-math for math in markdown or add math-inline and math-display classes in HTML.

unified is a project that transforms content with abstract syntax trees (ASTs). rehype adds support for HTML to unified. hast is the HTML AST that rehype uses. This is a rehype plugin that transforms hast.

When should I use this?

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

A different plugin, rehype-mathjax, is similar but uses MathJax instead.

Install

This package is ESM only. In Node.js (version 12.20+, 14.14+, or 16.0+), install with npm:

npm install rehype-katex

In Deno with esm.sh:

import rehypeKatex from "https://esm.sh/rehype-katex@6";

In browsers with esm.sh:

<script type="module">
  import rehypeKatex from "https://esm.sh/rehype-katex@6?bundle";
</script>

Use

Say we have the following file example.html:

<p>
  Lift(<span class="math math-inline">L</span>) can be determined by Lift
  Coefficient (<span class="math math-inline">C_L</span>) like the following
  equation.
</p>

<div class="math math-display">L = \frac{1}{2} \rho v^2 S C_L</div>

And our module example.js looks as follows:

import { read } from "to-vfile";
import { unified } from "unified";
import rehypeParse from "rehype-parse";
import rehypeKatex from "rehype-katex";
import rehypeDocument from "rehype-document";
import rehypeStringify from "rehype-stringify";

const file = await unified()
  .use(rehypeParse, { fragment: true })
  .use(rehypeKatex)
  .use(rehypeDocument, {
    css: "https://cdn.jsdelivr.net/npm/[email protected]/dist/katex.min.css",
  })
  .use(rehypeStringify)
  .process(await read("example.html"));

console.log(String(file));

Now running node example.js yields:

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <title>example</title>
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <link
      rel="stylesheet"
      href="https://cdn.jsdelivr.net/npm/[email protected]/dist/katex.min.css"
    />
  </head>
  <body>
    <p>
      Lift(<span class="math math-inline"><span class="katex">…</span></span
      >) can be determined by Lift Coefficient (<span class="math math-inline"
        ><span class="katex">…</span></span
      >) like the following equation.
    </p>
    <div class="math math-display"><span class="katex-display">…</span></div>
  </body>
</html>

API

This package exports no identifiers. The default export is rehypeKatex.

`unified().use(rehypeKatex[, options])`

Transform <span class="math-inline"> and <div class="math-display"> with KaTeX.

`options`

Configuration (optional). All options, except for displayMode, are passed to KaTeX.

`options.throwOnError`

Throw if a KaTeX parse error occurs (boolean, default: false). See KaTeX options.

CSS

The HTML produced by KaTeX requires CSS to render correctly. You should use katex.css somewhere on the page where the math is shown to style it properly. At the time of writing, the last version is:

<link
  rel="stylesheet"
  href="https://cdn.jsdelivr.net/npm/[email protected]/dist/katex.min.css"
  integrity="sha384-Xi8rHCmBmhbuyyhbI88391ZKP2dmfnOl4rT9ZfRI7mLTdk1wblIUnrIq35nqwEvC"
  crossorigin="anonymous"
/>

Syntax tree

This plugin transforms elements with a class name of either math-inline and/or math-display.

Types

This package is fully typed with TypeScript. An extra Options type is exported, which models the accepted options.

Compatibility

Projects maintained by the unified collective are compatible with all maintained versions of Node.js. As of now, that is Node.js 12.20+, 14.14+, and 16.0+. Our projects sometimes work with older versions, but this is not guaranteed.

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

Security

Using rehype-katex should be safe assuming that you trust KaTeX. Any vulnerability in it could open you to a cross-site scripting (XSS) attack. Always be wary of user input and use rehype-sanitize.

When you don’t trust user content but do trust KaTeX, you can allow the classes added by remark-math while disallowing anything else in the rehype-sanitize schema, and run rehype-katex afterwards. Like so:

import rehypeSanitize, { defaultSchema } from "rehype-sanitize";

const mathSanitizeSchema = {
  ...defaultSchema,
  attributes: {
    ...defaultSchema.attributes,
    div: [
      ...defaultSchema.attributes.div,
      ["className", "math", "math-display"],
    ],
    span: [["className", "math", "math-inline"]],
  },
};

// …

unified()
  // …
  .use(rehypeSanitize, mathSanitizeSchema)
  .use(rehypeKatex);
// …

rehype-mathjax — same but with MathJax
rehype-highlight — highlight code blocks
rehype-autolink-headings — add links to headings
rehype-sanitize — sanitize HTML
rehype-document — wrap a document around the tree

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.

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