rehype-pre-language

This package is a unified (rehype) plugin to add language information of <code> element into <pre> element as a property.

unified is a project that transforms content with abstract syntax trees (ASTs) using the new parser micromark. remark adds support for markdown to unified. mdast is the Markdown Abstract Syntax Tree (AST) which is a specification for representing markdown in a syntax tree. rehype is a tool that transforms HTML with plugins. hast stands for HTML Abstract Syntax Tree (HAST) that rehype uses.

This plugin finds the <code> elements in hast, takes the language information and adds the language into <pre> element as "className" property by default or as a property provided in options.

When should I use this?

This plugin rehype-pre-language is useful if there is no language information in <pre> element but <code> element like <pre><code className="language-typescript"></pre>, and you need <pre> element to have language information.

Installation

This package is suitable for ESM only. In Node.js (version 16+), install with npm:

npm install rehype-pre-language

yarn add rehype-pre-language

Usage

Say we have the following markdown file, example.md:

```javascript
const me = "ipikuka";
```

And our module, example.js, looks as follows:

import { read } from "to-vfile";
import remark from "remark";
import gfm from "remark-gfm";
import remarkRehype from "remark-rehype";
import rehypeStringify from "rehype-stringify";
import rehypePreLanguage from "rehype-pre-language";

main();

async function main() {
  const file = await remark()
    .use(gfm)
    .use(remarkRehype)
    .use(rehypePreLanguage)
    .use(rehypeStringify)
    .process(await read("example.md"));

  console.log(String(file));
}

Now, running node example.js you see that the <pre> element has a "class" with language information:

<pre class="javascript">
  <code class="language-javascript">const me = "ipikuka";</code>
</pre>

Without rehype-pre-language, the <pre> element wouldn't have a language information:

<pre>
  <code class="language-javascript">const me = "ipikuka";</code>
</pre>

Options

There is one string option which is a property of <pre> element in which the language information is going to be passed.

type PreLanguageOption = string; // the default is "className"

use(rehypePreLanguage, PreLanguageOption);

Examples:

// adds the language information into "className" of <pre> element as default
use(rehypePreLanguage);

// adds the language information into "className" of <pre> element
use(rehypePreLanguage, "className");

// adds the language information into "data-language" property of <pre> element
use(rehypePreLanguage, "data-language");

Syntax tree

This plugin modifies the hast (HTML abstract syntax tree).

Types

This package is fully typed with TypeScript.

The plugin exports the type PreLanguageOption.

Compatibility

This plugin works with rehype-parse version 1+, rehype-stringify version 1+, rehype version 1+, and unified version 4+.

Security

Use of rehype-pre-language involves rehype (hast), but doesn't lead to cross-site scripting (XSS) attacks.

My Plugins

I like to contribute the Unified / Remark / MDX ecosystem, so I recommend you to have a look my plugins.

My Remark Plugins

remark-flexible-code-titles – Remark plugin to add titles or/and containers for the code blocks with customizable properties
remark-flexible-containers – Remark plugin to add custom containers with customizable properties in markdown
remark-ins – Remark plugin to add ins element in markdown
remark-flexible-paragraphs – Remark plugin to add custom paragraphs with customizable properties in markdown
remark-flexible-markers – Remark plugin to add custom mark element with customizable properties in markdown
remark-flexible-toc – Remark plugin to expose the table of contents via vfile.data or via an option reference
remark-mdx-remove-esm – Remark plugin to remove import and/or export statements (mdxjsEsm)

My Rehype Plugins

rehype-pre-language – Rehype plugin to add language information as a property to pre element
rehype-highlight-code-lines – Rehype plugin to add line numbers to code blocks and allow highlighting of desired code lines
rehype-code-meta – Rehype plugin to copy code.data.meta to code.properties.metastring
rehype-image-toolkit – Rehype plugin to enhance Markdown image syntax ![]() and Markdown/MDX media elements (<img>, <audio>, <video>) by auto-linking bracketed or parenthesized image URLs, wrapping them in <figure> with optional captions, unwrapping images/videos/audio from paragraph, parsing directives in title for styling and adding attributes, and dynamically converting images into <video> or <audio> elements based on file extension.

My Recma Plugins

recma-mdx-escape-missing-components – Recma plugin to set the default value () => null for the Components in MDX in case of missing or not provided so as not to throw an error
recma-mdx-change-props – Recma plugin to change the props parameter into the _props in the function _createMdxContent(props) {/* */} in the compiled source in order to be able to use {props.foo} like expressions. It is useful for the next-mdx-remote or next-mdx-remote-client users in nextjs applications.
recma-mdx-change-imports – Recma plugin to convert import declarations for assets and media with relative links into variable declarations with string URLs, enabling direct asset URL resolution in compiled MDX.
recma-mdx-import-media – Recma plugin to turn media relative paths into import declarations for both markdown and html syntax in MDX.
recma-mdx-import-react – Recma plugin to ensure getting React instance from the arguments and to make the runtime props {React, jsx, jsxs, jsxDev, Fragment} is available in the dynamically imported components in the compiled source of MDX.
recma-mdx-html-override – Recma plugin to allow selected raw HTML elements to be overridden via MDX components.
recma-mdx-interpolate – Recma plugin to enable interpolation of identifiers wrapped in curly braces within the alt, src, href, and title attributes of markdown link and image syntax in MDX.

Package detail