hast-util-raw

What is hast-util-raw?

The hast-util-raw package is a utility for working with HAST (Hypertext Abstract Syntax Tree) trees. It can parse and transform raw HTML into a HAST tree, allowing for manipulation and analysis of the structure of HTML documents. This package is particularly useful for developers working with virtual DOMs or needing to preprocess or clean HTML content programmatically.

What are hast-util-raw's main functionalities?

Parsing HTML to HAST

This feature allows for the parsing of HTML strings embedded within HAST trees. The `raw` function takes a HAST tree that may contain raw HTML as part of its nodes and returns a new HAST tree with the raw HTML parsed into HAST nodes. This is useful for integrating unescaped HTML strings into a HAST-based workflow.

const raw = require('hast-util-raw');
const h = require('hastscript');
const tree = h('div', [h('span', 'Hello'), '<strong>world!</strong>']);
const result = raw(tree);

Transforming HAST with embedded raw HTML

This demonstrates how `hast-util-raw` can transform a HAST tree that includes a 'raw' node containing HTML into a fully parsed HAST structure. This is particularly useful for scenarios where raw HTML is mixed with HAST content and a uniform HAST structure is needed for further processing.

const raw = require('hast-util-raw');
const u = require('unist-builder');
const tree = u('root', [u('element', {tagName: 'div'}, [u('text', 'Some text'), u('raw', '<span>More text</span>')])]);
const result = raw(tree);

Other packages similar to hast-util-raw

rehype-parse

Similar to hast-util-raw, `rehype-parse` is used for parsing HTML into HAST. However, `rehype-parse` is more focused on being a full HTML parser as part of the rehype ecosystem, offering more comprehensive parsing options and better integration with rehype plugins.

README

hast-util-raw

hast utility to parse the tree and semistandard raw nodes (strings of HTML) again, keeping positional info okay.

Contents

• What is this?
• When should I use this?
• Install
• Use
• API
  • Options
  • raw(tree, options)
• Types
• Compatibility
• Security
• Related
• Contribute
• License

What is this?

This package is a utility to parse a document again. It passes each node and embedded raw HTML through an HTML parser (parse5), to recreate a tree exactly as how a browser would parse it, while keeping the original data and positional info intact.

When should I use this?

This utility is particularly useful when coming from markdown and wanting to support HTML embedded inside that markdown (which requires passing allowDangerousHtml: true to mdast-util-to-hast). Markdown dictates how, say, a list item or emphasis can be parsed. We can use that to turn the markdown syntax tree into an HTML syntax tree. But markdown also dictates that things that look like HTML, are passed through untouched, even when it just looks like XML but doesn’t really make sense, so we can’t normally use these strings of “HTML” to create an HTML syntax tree. This utility can. It can be used to take those strings of HTML and include them into the syntax tree as actual nodes.

If your final result is HTML and you trust content, then “strings” are fine (you can pass allowDangerousHtml: true to hast-util-to-html, which passes HTML through untouched). But there are two main cases where a proper syntax tree is preferred:

• hast utilities need a proper syntax tree as they operate on actual nodes to inspect or transform things, they can’t operate on strings of HTML
• other output formats (React, MDX, etc) need actual nodes and can’t handle strings of HTML

The plugin rehype-raw wraps this utility at a higher-level (easier) abstraction.

Install

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

npm install hast-util-raw

In Deno with esm.sh:

import {raw} from 'https://esm.sh/hast-util-raw@9'

In browsers with esm.sh:

<script type="module">
  import {raw} from 'https://esm.sh/hast-util-raw@9?bundle'
</script>

Use

import {h} from 'hastscript'
import {raw} from 'hast-util-raw'

const tree = h('div', [h('h1', ['Foo ', h('h2', 'Bar'), ' Baz'])])

const reformatted = raw(tree)

console.log(reformatted)

Yields:

{ type: 'element',
  tagName: 'div',
  properties: {},
  children:
   [ { type: 'element',
       tagName: 'h1',
       properties: {},
       children: [Object] },
     { type: 'element',
       tagName: 'h2',
       properties: {},
       children: [Object] },
     { type: 'text', value: ' Baz' } ] }

API

Options

Configuration.

Fields

• file? (VFile | null | undefined) — corresponding virtual file representing the input document (optional)

• passThrough? (Array<string> | null | undefined)

  List of custom hast node types to pass through (as in, keep) (optional).

  If the passed through nodes have children, those children are expected to be hast again and will be handled.

• tagfilter? (boolean | null | undefined)

  Whether to disallow irregular tags in raw nodes according to GFM tagfilter (default: false).

  This affects the following tags, grouped by their kind:

  • RAWTEXT: iframe, noembed, noframes, style, xmp
  • RCDATA: textarea, title
  • SCRIPT_DATA: script
  • PLAINTEXT: plaintext When you know that you do not want authors to write these tags, you can enable this option to prevent their use from running amok.

  See: Disallowed Raw HTML in cmark-gfm.

raw(tree, options)

Pass a hast tree through an HTML parser, which will fix nesting, and turn raw nodes into actual nodes.

Parameters

• tree (Root | RootContent) — original hast tree to transform
• options? (Options | null | undefined) — configuration (optional)

Returns

Parsed again tree (Root | RootContent).

Types

This package is fully typed with TypeScript. It exports the additional type Options.

The Raw node type is registered by and exposed from mdast-util-to-hast.

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, hast-util-raw@^9, compatible with Node.js 16.

Security

Use of hast-util-raw can open you up to a cross-site scripting (XSS) attack as raw nodes are unsafe. The following example shows how a raw node is used to inject a script that runs when loaded in a browser.

raw(u('root', [u('raw', '<script>alert(1)</script>')]))

Yields:

<script>alert(1)</script>

Either do not use this utility in combination with user input, or use hast-util-santize.

Related

• mdast-util-to-hast — transform mdast to hast
• rehype-raw — rehype plugin

Contribute

See contributing.md in syntax-tree/.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