458 lines
12 KiB
Plaintext
458 lines
12 KiB
Plaintext
# hast-util-to-html
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[![Build][build-badge]][build]
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[![Coverage][coverage-badge]][coverage]
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[![Downloads][downloads-badge]][downloads]
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[![Size][size-badge]][size]
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[![Sponsors][sponsors-badge]][collective]
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[![Backers][backers-badge]][collective]
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[![Chat][chat-badge]][chat]
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[hast][] utility to serialize hast as HTML.
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## Contents
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* [What is this?](#what-is-this)
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* [When should I use this?](#when-should-i-use-this)
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* [Install](#install)
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* [Use](#use)
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* [API](#api)
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* [`toHtml(tree[, options])`](#tohtmltree-options)
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* [`CharacterReferences`](#characterreferences)
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* [`Options`](#options)
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* [`Quote`](#quote-1)
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* [`Space`](#space-1)
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* [Syntax](#syntax)
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* [Types](#types)
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* [Compatibility](#compatibility)
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* [Security](#security)
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* [Related](#related)
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* [Contribute](#contribute)
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* [License](#license)
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## What is this?
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This package is a utility that turns a hast tree into a string of HTML.
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## When should I use this?
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You can use this utility when you want to get the serialized HTML that is
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represented by the syntax tree, either because you’re done with the syntax
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tree, or because you’re integrating with another tool that does not support
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syntax trees.
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This utility has many options to configure how the HTML is serialized.
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These options help when building tools that make output pretty (such as
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formatters) or ugly (such as minifiers).
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The utility [`hast-util-from-html`][hast-util-from-html] does the inverse of
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this utility.
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It turns HTML into hast.
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The rehype plugin [`rehype-stringify`][rehype-stringify] wraps this utility to
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also serialize HTML at a higher-level (easier) abstraction.
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## Install
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This package is [ESM only][esm].
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In Node.js (version 16+), install with [npm][]:
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```sh
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npm install hast-util-to-html
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```
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In Deno with [`esm.sh`][esmsh]:
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```js
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import {toHtml} from "https://esm.sh/hast-util-to-html@9"
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```
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In browsers with [`esm.sh`][esmsh]:
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```html
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<script type="module">
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import {toHtml} from "https://esm.sh/hast-util-to-html@9?bundle"
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</script>
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```
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## Use
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<details><summary>Show install command for this example</summary>
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```sh
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npm install hastscript hast-util-to-html
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```
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</details>
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```js
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import {h} from 'hastscript'
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import {toHtml} from 'hast-util-to-html'
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var tree = h('.alpha', [
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'bravo ',
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h('b', 'charlie'),
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' delta ',
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h('a.echo', {download: true}, 'foxtrot')
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])
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console.log(toHtml(tree))
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```
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Yields:
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```html
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<div class="alpha">bravo <b>charlie</b> delta <a class="echo" download>foxtrot</a></div>
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```
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## API
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This package exports the identifier [`toHtml`][api-to-html].
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There is no default export.
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### `toHtml(tree[, options])`
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Serialize hast as HTML.
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###### Parameters
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* `tree` ([`Node`][node] or `Array<Node>`)
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— tree to serialize
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* `options` ([`Options`][api-options], optional)
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— configuration
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###### Returns
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Serialized HTML (`string`).
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### `CharacterReferences`
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How to serialize character references (TypeScript type).
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##### Fields
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###### `useNamedReferences`
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Prefer named character references (`&`) where possible (`boolean`, default:
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`false`).
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###### `omitOptionalSemicolons`
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Whether to omit semicolons when possible (`boolean`, default: `false`).
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> ⚠️ **Note**: this creates what HTML calls “parse errors” but is otherwise
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> still valid HTML — don’t use this except when building a minifier.
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> Omitting semicolons is possible for certain named and numeric references in
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> some cases.
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###### `useShortestReferences`
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Prefer the shortest possible reference, if that results in less bytes
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(`boolean`, default: `false`).
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> ⚠️ **Note**: `useNamedReferences` can be omitted when using
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> `useShortestReferences`.
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### `Options`
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Configuration (TypeScript type).
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##### Fields
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###### `allowDangerousCharacters`
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Do not encode some characters which cause XSS vulnerabilities in older browsers
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(`boolean`, default: `false`).
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> ⚠️ **Danger**: only set this if you completely trust the content.
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###### `allowDangerousHtml`
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Allow `raw` nodes and insert them as raw HTML (`boolean`, default: `false`).
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When `false`, `Raw` nodes are encoded.
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> ⚠️ **Danger**: only set this if you completely trust the content.
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###### `allowParseErrors`
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Do not encode characters which cause parse errors (even though they work), to
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save bytes (`boolean`, default: `false`).
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Not used in the SVG space.
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> 👉 **Note**: intentionally creates parse errors in markup (how parse errors
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> are handled is well defined, so this works but isn’t pretty).
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###### `bogusComments`
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Use “bogus comments” instead of comments to save byes: `<?charlie>` instead of
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`<!--charlie-->` (`boolean`, default: `false`).
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> 👉 **Note**: intentionally creates parse errors in markup (how parse errors
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> are handled is well defined, so this works but isn’t pretty).
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###### `characterReferences`
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Configure how to serialize character references
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([`CharacterReferences`][api-character-references], optional).
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###### `closeEmptyElements`
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Close SVG elements without any content with slash (`/`) on the opening tag
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instead of an end tag: `<circle />` instead of `<circle></circle>` (`boolean`,
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default: `false`).
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See `tightSelfClosing` to control whether a space is used before the slash.
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Not used in the HTML space.
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###### `closeSelfClosing`
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Close self-closing nodes with an extra slash (`/`): `<img />` instead of
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`<img>` (`boolean`, default: `false`).
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See `tightSelfClosing` to control whether a space is used before the slash.
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Not used in the SVG space.
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###### `collapseEmptyAttributes`
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Collapse empty attributes: get `class` instead of `class=""` (`boolean`,
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default: `false`).
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Not used in the SVG space.
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> 👉 **Note**: boolean attributes (such as `hidden`) are always collapsed.
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###### `omitOptionalTags`
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Omit optional opening and closing tags (`boolean`, default: `false`).
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For example, in `<ol><li>one</li><li>two</li></ol>`, both `</li>` closing tags
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can be omitted.
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The first because it’s followed by another `li`, the last because it’s followed
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by nothing.
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Not used in the SVG space.
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###### `preferUnquoted`
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Leave attributes unquoted if that results in less bytes (`boolean`, default:
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`false`).
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Not used in the SVG space.
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###### `quote`
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Preferred quote to use ([`Quote`][api-quote], default: `'"'`).
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###### `quoteSmart`
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Use the other quote if that results in less bytes (`boolean`, default: `false`).
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###### `space`
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Which space the document is in ([`Space`][api-space], default: `'html'`).
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When an `<svg>` element is found in the HTML space, this package already
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automatically switches to and from the SVG space when entering and exiting it.
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> 👉 **Note**: hast is not XML.
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> It supports SVG as embedded in HTML.
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> It does not support the features available in XML.
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> Passing SVG might break but fragments of modern SVG should be fine.
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> Use [`xast`][xast] if you need to support SVG as XML.
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###### `tightAttributes`
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Join attributes together, without whitespace, if possible: get
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`class="a b"title="c d"` instead of `class="a b" title="c d"` to save bytes
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(`boolean`, default: `false`).
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Not used in the SVG space.
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> 👉 **Note**: intentionally creates parse errors in markup (how parse errors
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> are handled is well defined, so this works but isn’t pretty).
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###### `tightCommaSeparatedLists`
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Join known comma-separated attribute values with just a comma (`,`), instead of
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padding them on the right as well (`,␠`, where `␠` represents a space)
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(`boolean`, default: `false`).
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###### `tightDoctype`
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Drop unneeded spaces in doctypes: `<!doctypehtml>` instead of `<!doctype html>`
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to save bytes (`boolean`, default: `false`).
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> 👉 **Note**: intentionally creates parse errors in markup (how parse errors
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> are handled is well defined, so this works but isn’t pretty).
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###### `tightSelfClosing`
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Do not use an extra space when closing self-closing elements: `<img/>` instead
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of `<img />` (`boolean`, default: `false`).
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> 👉 **Note**: only used if `closeSelfClosing: true` or
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> `closeEmptyElements: true`.
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###### `upperDoctype`
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Use a `<!DOCTYPE…` instead of `<!doctype…` (`boolean`, default: `false`).
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Useless except for XHTML.
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###### `voids`
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Tag names of elements to serialize without closing tag (`Array<string>`,
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default: [`html-void-elements`][html-void-elements]).
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Not used in the SVG space.
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> 👉 **Note**: It’s highly unlikely that you want to pass this, because hast is
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> not for XML, and HTML will not add more void elements.
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### `Quote`
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HTML quotes for attribute values (TypeScript type).
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###### Type
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```ts
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type Quote = '"' | "'"
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```
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### `Space`
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Namespace (TypeScript type).
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###### Type
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```ts
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type Space = 'html' | 'svg'
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```
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## Syntax
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HTML is serialized according to WHATWG HTML (the living standard), which is also
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followed by browsers such as Chrome and Firefox.
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## Types
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This package is fully typed with [TypeScript][].
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It exports the additional types
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[`CharacterReferences`][api-character-references],
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[`Options`][api-options],
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[`Quote`][api-quote], and
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[`Space`][api-space].
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## Compatibility
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Projects maintained by the unified collective are compatible with maintained
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versions of Node.js.
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When we cut a new major release, we drop support for unmaintained versions of
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Node.
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This means we try to keep the current release line, `hast-util-to-html@^9`,
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compatible with Node.js 16.
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## Security
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Use of `hast-util-to-html` can open you up to a
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[cross-site scripting (XSS)][xss] attack if the hast tree is unsafe.
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Use [`hast-util-santize`][hast-util-sanitize] to make the hast tree safe.
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## Related
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* [`hast-util-sanitize`](https://github.com/syntax-tree/hast-util-sanitize)
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— sanitize hast
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## Contribute
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See [`contributing.md`][contributing] in [`syntax-tree/.github`][health] for
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ways to get started.
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See [`support.md`][support] for ways to get help.
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This project has a [code of conduct][coc].
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By interacting with this repository, organization, or community you agree to
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abide by its terms.
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## License
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[MIT][license] © [Titus Wormer][author]
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<!-- Definitions -->
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[build-badge]: https://github.com/syntax-tree/hast-util-to-html/workflows/main/badge.svg
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[build]: https://github.com/syntax-tree/hast-util-to-html/actions
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[coverage-badge]: https://img.shields.io/codecov/c/github/syntax-tree/hast-util-to-html.svg
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[coverage]: https://codecov.io/github/syntax-tree/hast-util-to-html
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[downloads-badge]: https://img.shields.io/npm/dm/hast-util-to-html.svg
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[downloads]: https://www.npmjs.com/package/hast-util-to-html
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[size-badge]: https://img.shields.io/badge/dynamic/json?label=minzipped%20size&query=$.size.compressedSize&url=https://deno.bundlejs.com/?q=hast-util-to-html
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[size]: https://bundlejs.com/?q=hast-util-to-html
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[sponsors-badge]: https://opencollective.com/unified/sponsors/badge.svg
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[backers-badge]: https://opencollective.com/unified/backers/badge.svg
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[collective]: https://opencollective.com/unified
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[chat-badge]: https://img.shields.io/badge/chat-discussions-success.svg
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[chat]: https://github.com/syntax-tree/unist/discussions
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[npm]: https://docs.npmjs.com/cli/install
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[esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c
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[esmsh]: https://esm.sh
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[typescript]: https://www.typescriptlang.org
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[license]: license
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[author]: https://wooorm.com
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[health]: https://github.com/syntax-tree/.github
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[contributing]: https://github.com/syntax-tree/.github/blob/main/contributing.md
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[support]: https://github.com/syntax-tree/.github/blob/main/support.md
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[coc]: https://github.com/syntax-tree/.github/blob/main/code-of-conduct.md
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[xss]: https://en.wikipedia.org/wiki/Cross-site_scripting
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[hast]: https://github.com/syntax-tree/hast
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[node]: https://github.com/syntax-tree/hast#nodes
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[html-void-elements]: https://github.com/wooorm/html-void-elements
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[hast-util-sanitize]: https://github.com/syntax-tree/hast-util-sanitize
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[hast-util-from-html]: https://github.com/syntax-tree/hast-util-from-html
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[rehype-stringify]: https://github.com/rehypejs/rehype/tree/main/packages/rehype-stringify#readme
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[xast]: https://github.com/syntax-tree/xast
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[api-to-html]: #tohtmltree-options
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[api-character-references]: #characterreferences
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[api-options]: #options
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[api-space]: #space-1
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[api-quote]: #quote-1
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