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hast-util-raw

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

Contents

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 12.20+, 14.14+, 16.0+, or 18.0+), install with npm:

npm install hast-util-raw

In Deno with esm.sh:

import {raw} from 'https://esm.sh/hast-util-raw@7'

In browsers with esm.sh:

<script type="module">
  import {raw} from 'https://esm.sh/hast-util-raw@7?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

This package exports the identifier raw. There is no default export.

raw(tree[, file][, options])

Parse the tree and raw nodes (strings of HTML) again, keeping positional info okay.

👉 Note: tree should have positional info and file, when given, must be a vfile corresponding to tree.

options

Configuration (optional).

options.passThrough

List of custom hast node types to pass through (keep) in hast (Array<string>, default: []). If the passed through nodes have children, those children are expected to be hast and will be handled by this utility.

Types

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

It also registers the Raw node type with @types/hast. If you’re working with the syntax tree, make sure to import this utility somewhere in your types, as that registers the new node types in the tree.

/**
 * @typedef {import('hast-util-raw')}
 */

import {visit} from 'unist-util-visit'

/** @type {import('hast').Root} */
const tree = getHastNodeSomeHow()

visit(tree, (node) => {
  // `node` can now be a `raw` node.
})

Compatibility

Projects maintained by the unified collective are compatible with all maintained versions of Node.js. As of now, that is Node.js 12.20+, 14.14+, 16.0+, and 18.0+. Our projects sometimes work with older versions, but this is not guaranteed.

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

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