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readme.md

rehype-javascript-to-bottom

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rehype plugin to move JavaScript <script>s to the end of the body.

Contents

What is this?

This package is a plugin that can improve performance by decreasing the time to first render.

When should I use this?

You can use this plugin when you want to improve the speed of HTML documents.

Install

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

npm install rehype-javascript-to-bottom

In Deno with esm.sh:

import rehypeJavaScriptToBottom from 'https://esm.sh/rehype-javascript-to-bottom@4'

In browsers with esm.sh:

<script type="module">
  import rehypeJavaScriptToBottom from 'https://esm.sh/rehype-javascript-to-bottom@4?bundle'
</script>

Use

On the API:

import rehypeJavaScriptToBottom from 'rehype-javascript-to-bottom'
import rehypeParse from 'rehype-parse'
import rehypeStringify from 'rehype-stringify'
import {read} from 'to-vfile'
import {unified} from 'unified'

const file = await unified()
  .use(rehypeParse)
  .use(rehypeJavaScriptToBottom)
  .use(rehypeStringify)
  .process(await read('index.html'))

console.log(String(file))

On the CLI:

rehype input.html --use rehype-javascript-to-bottom --output output.html

On the CLI in a config file (here a package.json):

 …
 "rehype": {
   "plugins": [
     …
+    "rehype-javascript-to-bottom",
     …
   ]
 }
 …

API

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

unified().use(rehypeJavaScriptToBottom[, options])

Move JavaScript <script>s to the end of <body>.

Parameters
  • options (Options, optional) — configuration
Returns

Transform (Transformer).

Filter

Filter scripts that would be moved (TypeScript type).

Parameters
  • node (Element) — script element
Returns

Whether to move the script (true) or not (boolean, optional).

Options

Configuration (TypeScript type).

Fields
  • filter (Filter, optional) — filter scripts that would otherwise be moved

Example

In
<!doctype html><html><head><script src="index.js"></script></head><body></body></html>
Out
<!doctype html><html><head></head><body><script src="index.js"></script></body></html>

Syntax

HTML is parsed according to WHATWG HTML (the living standard), which is also followed by all browsers.

Syntax tree

The syntax tree used is hast.

Types

This package is fully typed with TypeScript.

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-javascript-to-bottom@^4, compatible with Node.js 16.

Security

As rehype works on HTML and improper use of HTML can open you up to a cross-site scripting (XSS) attack, use of rehype can also be unsafe. Use rehype-sanitize to make the tree safe.

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

MIT © Titus Wormer