hast-util-to-html

What is hast-util-to-html?

The hast-util-to-html package is a utility for converting HAST (Hypertext Abstract Syntax Tree) syntax trees to HTML strings. This is particularly useful in the context of unified.js ecosystem for processing HTML content, enabling developers to easily transform markdown or other formats into HTML after processing them through various plugins.

What are hast-util-to-html's main functionalities?

Convert HAST to HTML

This feature allows you to convert a HAST tree to an HTML string. The code sample demonstrates converting a simple paragraph element with text content into its HTML string representation.

const toHtml = require('hast-util-to-html');
const hast = {
  type: 'element',
  tagName: 'p',
  properties: {},
  children: [{type: 'text', value: 'Hello, world!'}]
};
console.log(toHtml(hast));

Other packages similar to hast-util-to-html

rehype-stringify

Part of the rehype ecosystem, which is built on top of unified, rehype-stringify converts HAST to HTML. It is similar to hast-util-to-html but is typically used as a rehype plugin, offering a more integrated experience within the rehype ecosystem.

remark-html

While not directly converting HAST to HTML, remark-html is a plugin for remark (a markdown processor) that allows markdown to be converted to HTML. It serves a similar end goal of transforming content into HTML, but it starts with markdown instead of HAST.

README

hast-util-to-html

hast utility to serialize to HTML.

Install

npm:

npm install hast-util-to-html

Use

var h = require('hastscript')
var toHtml = require('hast-util-to-html')

var tree = h('.alpha', [
  'bravo ',
  h('b', 'charlie'),
  ' delta ',
  h('a.echo', {download: true}, 'foxtrot')
])

console.log(toHtml(tree))

Yields:

<div class="alpha">bravo <b>charlie</b> delta <a class="echo" download>foxtrot</a></div>

API

toHtml(tree[, options])

Serialize the given hast tree (or list of nodes).

options.space

Whether the root of the tree is in the 'html' or 'svg' space (enum, 'svg' or 'html', default: 'html').

If an svg element is found in the HTML space, toHtml automatically switches to the SVG space when entering the element, and switches back when exiting.

options.entities

Configuration for stringify-entities (Object, default: {}). Do not use escapeOnly, attribute, or subset (toHtml already passes those, so they won’t work). However, useNamedReferences, useShortestReferences, and omitOptionalSemicolons are all fine.

options.voids

Tag names of elements to serialize without closing tag (Array.<string>, default: html-void-elements).

Not used in the SVG space.

options.upperDoctype

Use a <!DOCTYPE… instead of <!doctype…. Useless except for XHTML (boolean, default: false).

options.quote

Preferred quote to use ('"' or '\'', default: '"').

options.quoteSmart

Use the other quote if that results in less bytes (boolean, default: false).

options.preferUnquoted

Leave attributes unquoted if that results in less bytes (boolean, default: false).

Not used in the SVG space.

options.omitOptionalTags

Omit optional opening and closing tags (boolean, default: false). For example, in <ol><li>one</li><li>two</li></ol>, both </li> closing tags can be omitted. The first because it’s followed by another li, the last because it’s followed by nothing.

Not used in the SVG space.

options.collapseEmptyAttributes

Collapse empty attributes: get class instead of class="" (boolean, default: false). Note: boolean attributes, such as hidden, are always collapsed.

Not used in the SVG space.

options.closeSelfClosing

Close self-closing nodes with an extra slash (/): <img /> instead of <img> (boolean, default: false). See tightSelfClosing to control whether a space is used before the slash.

Not used in the SVG space.

options.closeEmptyElements

Close SVG elements without any content with slash (/) on the opening tag instead of an end tag: <circle /> instead of <circle></circle> (boolean, default: false). See tightSelfClosing to control whether a space is used before the slash.

Not used in the HTML space.

options.tightSelfClosing

Do not use an extra space when closing self-closing elements: <img/> instead of <img /> (boolean, default: false). Note: Only used if closeSelfClosing: true or closeEmptyElements: true.

options.tightCommaSeparatedLists

Join known comma-separated attribute values with just a comma (,), instead of padding them on the right as well (,·, where · represents a space) (boolean, default: false).

options.tightAttributes

Join attributes together, without white-space, if possible: get class="a b"title="c d" instead of class="a b" title="c d" to save bytes (boolean, default: false). Note: creates invalid (but working) markup.

Not used in the SVG space.

options.tightDoctype

Drop unneeded spaces in doctypes: <!doctypehtml> instead of <!doctype html> to save bytes (boolean, default: false). Note: creates invalid (but working) markup.

options.bogusComments

Use “bogus comments” instead of comments to save byes: <?charlie> instead of <!--charlie--> (boolean, default: false). Note: creates invalid (but working) markup.

options.allowParseErrors

Do not encode characters which cause parse errors (even though they work), to save bytes (boolean, default: false). Note: creates invalid (but working) markup.

Not used in the SVG space.

options.allowDangerousCharacters

Do not encode some characters which cause XSS vulnerabilities in older browsers (boolean, default: false). Note: Only set this if you completely trust the content.

options.allowDangerousHtml

Allow raw nodes and insert them as raw HTML. When falsey, encodes raw nodes (boolean, default: false). Note: Only set this if you completely trust the content.

Security

Use of hast-util-to-html can open you up to a cross-site scripting (XSS) attack if the hast tree is unsafe. Use hast-util-santize to make the hast tree safe.

Related

• hast-util-sanitize — Sanitize hast nodes
• rehype-stringify — Wrapper around this project for rehype

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