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rehype plugin to highlight code blocks in HTML with Prism (via refractor)
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README.md

rehype-prism

Build Status

rehype plugin to highlight code blocks in HTML with Prism (via refractor).

(If you would like to highlight code blocks with highlight.js, instead, check out rehype-highlight.)

Best suited for usage in Node. If you would like to perform syntax highlighting in the browser, you should look into less heavy ways to use refractor.

Installation

npm install @mapbox/rehype-prism

API

rehype().use(rehypePrism, [options])

Syntax highlights pre > code. Under the hood, it uses refractor, which is a virtual version of Prism.

The code language is configured by setting a language-{name} class on the <code> element. You can use any language supported by refractor.

If no language-{name} class is found on a <code> element, it will be skipped.

options

options.ignoreMissing

Type: boolean. Default: false.

By default, if {name} does not correspond to a language supported by refractor an error will be thrown.

If you would like to silently skip <code> elements with invalid languages, set this option to true.

Usage

Use this package as a rehype plugin.

Some examples of how you might do that:

const rehype = require('rehype');
const rehypePrism = require('rehype-prism');

rehype()
  .use(rehypePrism)
  .process(/* some html */);
const unified = require('unified');
const rehypeParse = require('rehype-parse');
const rehypePrism = require('rehype-prism');

unified()
  .use(rehypeParse)
  .use(rehypePrism)
  .processSync(/* some html */);

If you'd like to get syntax highlighting in Markdown, parse the Markdown (with remark-parse), convert it to rehype, then use this plugin.

const unified = require('unified');
const remarkParse = require('remark-parse');
const remarkRehype = require('remark-rehype');
const rehypePrism = require('rehype-prism');

unified()
  .use(remarkParse)
  .use(remarkRehype)
  .use(rehypePrism)
  .process(/* some markdown */);

FAQ

Why does rehype-prism copy the language- class to the <pre> tag?

Prism recommends adding the language- class to the <code> tag like this:

<pre><code class="language-css">p { color: red }</code></pre>

It bases this recommendation on the HTML5 spec. However, an undocumented behavior of their JavaScript is that, in the process of highlighting the code, they also copy the language- class to the <pre> tag:

<pre class="language-css"><code class="language-css"><span class="token selector">p</span> <span class="token punctuation">{</span> <span class="token property">color</span><span class="token punctuation">:</span> red <span class="token punctuation">}</span></code></pre>

This resulted in many Prism themes relying on this behavior by using CSS selectors like pre[class*="language-"]. So in order for people using rehype-prism to get the most out of these themes, we decided to do the same.

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