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rehype-format

rehype plugin to format HTML.

What is this?
When should I use this?
Install
Use
API
- unified().use(rehypeFormat[, options])
- Options
Examples
- Example: markdown input (remark)
- Example: tabs and blank lines (indent, blanks)
Types
Compatibility
Security
Related
Contribute
License

What is this?

This package is a unified (rehype) plugin to format whitespace in HTML. In short, it works as follows:

collapse all existing whitespace to either a line ending or a single space
remove those spaces and line endings if they do not contribute to the document
inject needed line endings
indent previously collapsed line endings properly

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 changes whitespace in hast.

When should I use this?

This package is useful when you want to improve the readability of HTML source code as it adds insignificant but pretty whitespace between elements. The package hast-util-format does the same as this plugin at the utility level. A different plugin, rehype-stringify, controls how HTML is actually printed: which quotes to use, whether to put a / on <img />, etc. Yet another project, rehype-minify, does the inverse: improve the size of HTML source code by making it hard to read.

Install

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

npm install rehype-format

In Deno with esm.sh:

import rehypeFormat from 'https://esm.sh/rehype-format@5'

In browsers with esm.sh:

<script type="module">
  import rehypeFormat from 'https://esm.sh/rehype-format@5?bundle'
</script>

Use

Say we have the following file index.html:

<!doCTYPE HTML><html>
 <head>
    <title>Hello!</title>
<meta charset=utf8>
      </head>
  <body><section>    <p>hi there</p>
     </section>
 </body>
</html>

…and our module example.js looks as follows:

import rehypeFormat from 'rehype-format'
import rehypeParse from 'rehype-parse'
import rehypeStringify from 'rehype-stringify'
import {read} from 'to-vfile'
import {unified} from 'unified'

const file = await read('index.html')

await unified()
  .use(rehypeParse)
  .use(rehypeFormat)
  .use(rehypeStringify)
  .process(file)

console.log(String(file))

…then running node example.js yields:

<!doctype html>
<html>
  <head>
    <title>Hello!</title>
    <meta charset="utf8">
  </head>
  <body>
    <section>
      <p>hi there</p>
    </section>
  </body>
</html>

API

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

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

Format whitespace in HTML.

Parameters

options (Options, optional) — configuration

Returns

Transform (Transformer).

`Options`

Configuration (TypeScript type).

Fields

blanks (Array<string>, default: []) — list of tag names to join with a blank line (default: []); these tags, when next to each other, are joined by a blank line (\n\n); for example, when ['head', 'body'] is given, a blank line is added between these two
indent (number, string, default: 2) — indentation per level (default: 2); when number, uses that amount of spaces; when string, uses that per indentation level
indentInitial (boolean, default: true) — whether to indent the first level (default: true); this is usually the <html>, thus not indenting head and body

Examples

Example: markdown input (remark)

The following example shows how remark and rehype can be combined to turn markdown into HTML, using this plugin to pretty print the HTML:

import rehypeDocument from 'rehype-document'
import rehypeFormat from 'rehype-format'
import rehypeStringify from 'rehype-stringify'
import remarkParse from 'remark-parse'
import remarkRehype from 'remark-rehype'
import {unified} from 'unified'

const file = await unified()
  .use(remarkParse)
  .use(remarkRehype)
  .use(rehypeDocument, {title: 'Neptune'})
  .use(rehypeFormat)
  .use(rehypeStringify)
  .process('# Hello, Neptune!')

console.log(String(file))

Yields:

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <title>Neptune</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
  </head>
  <body>
    <h1>Hello, Neptune!</h1>
  </body>
</html>

Example: tabs and blank lines (`indent`, `blanks`)

The following example shows how this plugin can format with tabs instead of spaces by passing the indent option and how blank lines can be added between certain elements:

import rehypeFormat from 'rehype-format'
import rehypeParse from 'rehype-parse'
import rehypeStringify from 'rehype-stringify'
import {unified} from 'unified'

const file = await unified()
  .use(rehypeParse)
  .use(rehypeFormat, {blanks: ['body', 'head'], indent: '\t'})
  .use(rehypeStringify)
  .process('<h1>Hi!</h1><p>Hello, Venus!</p>')

console.log(String(file))

Yields:

<html>
	<head></head>

	<body>
		<h1>Hi!</h1>
		<p>Hello, Venus!</p>
	</body>
</html>

👉 Note: the added tags (html, head, and body) do not come from this plugin. They’re instead added by rehype-parse, which in document mode (default), adds them according to the HTML spec.

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-format@5, compatible with Node.js 16.

This plugin works with rehype-parse version 3+, rehype-stringify version 3+, rehype version 5+, and unified version 6+.

Security

Use of rehype-format changes whitespace in the tree. Whitespace in <script>, <style>, <pre>, or <textarea> is not modified. If the tree is already safe, use of this plugin does not open you up for a cross-site scripting (XSS) attack. When in doubt, use rehype-sanitize.

rehype-minify — minify HTML
rehype-document — wrap a fragment in a document
rehype-sanitize — sanitize HTML
rehype-toc — add a table of contents (TOC)
rehype-section — wrap headings and their contents in sections

Contribute

See contributing.md in rehypejs/.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