# hast-util-to-html
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[hast][] utility to serialize hast as HTML.
## Contents
* [What is this?](#what-is-this)
* [When should I use this?](#when-should-i-use-this)
* [Install](#install)
* [Use](#use)
* [API](#api)
* [`toHtml(tree[, options])`](#tohtmltree-options)
* [`CharacterReferences`](#characterreferences)
* [`Options`](#options)
* [`Quote`](#quote-1)
* [`Space`](#space-1)
* [Syntax](#syntax)
* [Types](#types)
* [Compatibility](#compatibility)
* [Security](#security)
* [Related](#related)
* [Contribute](#contribute)
* [License](#license)
## What is this?
This package is a utility that turns a hast tree into a string of HTML.
## When should I use this?
You can use this utility when you want to get the serialized HTML that is
represented by the syntax tree, either because you’re done with the syntax
tree, or because you’re integrating with another tool that does not support
syntax trees.
This utility has many options to configure how the HTML is serialized.
These options help when building tools that make output pretty (such as
formatters) or ugly (such as minifiers).
The utility [`hast-util-from-html`][hast-util-from-html] does the inverse of
this utility.
It turns HTML into hast.
The rehype plugin [`rehype-stringify`][rehype-stringify] wraps this utility to
also serialize HTML at a higher-level (easier) abstraction.
## Install
This package is [ESM only][esm].
In Node.js (version 16+), install with [npm][]:
```sh
npm install hast-util-to-html
```
In Deno with [`esm.sh`][esmsh]:
```js
import {toHtml} from "https://esm.sh/hast-util-to-html@9"
```
In browsers with [`esm.sh`][esmsh]:
```html
```
## Use
Show install command for this example
```sh
npm install hastscript hast-util-to-html
```
```js
import {h} from 'hastscript'
import {toHtml} from 'hast-util-to-html'
var tree = h('.alpha', [
'bravo ',
h('b', 'charlie'),
' delta ',
h('a.echo', {download: true}, 'foxtrot')
])
console.log(toHtml(tree))
```
Yields:
```html
```
## API
This package exports the identifier [`toHtml`][api-to-html].
There is no default export.
### `toHtml(tree[, options])`
Serialize hast as HTML.
###### Parameters
* `tree` ([`Node`][node] or `Array`)
— tree to serialize
* `options` ([`Options`][api-options], optional)
— configuration
###### Returns
Serialized HTML (`string`).
### `CharacterReferences`
How to serialize character references (TypeScript type).
##### Fields
###### `useNamedReferences`
Prefer named character references (`&`) where possible (`boolean`, default:
`false`).
###### `omitOptionalSemicolons`
Whether to omit semicolons when possible (`boolean`, default: `false`).
> ⚠️ **Note**: this creates what HTML calls “parse errors” but is otherwise
> still valid HTML — don’t use this except when building a minifier.
> Omitting semicolons is possible for certain named and numeric references in
> some cases.
###### `useShortestReferences`
Prefer the shortest possible reference, if that results in less bytes
(`boolean`, default: `false`).
> ⚠️ **Note**: `useNamedReferences` can be omitted when using
> `useShortestReferences`.
### `Options`
Configuration (TypeScript type).
##### Fields
###### `allowDangerousCharacters`
Do not encode some characters which cause XSS vulnerabilities in older browsers
(`boolean`, default: `false`).
> ⚠️ **Danger**: only set this if you completely trust the content.
###### `allowDangerousHtml`
Allow `raw` nodes and insert them as raw HTML (`boolean`, default: `false`).
When `false`, `Raw` nodes are encoded.
> ⚠️ **Danger**: only set this if you completely trust the content.
###### `allowParseErrors`
Do not encode characters which cause parse errors (even though they work), to
save bytes (`boolean`, default: `false`).
Not used in the SVG space.
> 👉 **Note**: intentionally creates parse errors in markup (how parse errors
> are handled is well defined, so this works but isn’t pretty).
###### `bogusComments`
Use “bogus comments” instead of comments to save byes: `` instead of
`` (`boolean`, default: `false`).
> 👉 **Note**: intentionally creates parse errors in markup (how parse errors
> are handled is well defined, so this works but isn’t pretty).
###### `characterReferences`
Configure how to serialize character references
([`CharacterReferences`][api-character-references], optional).
###### `closeEmptyElements`
Close SVG elements without any content with slash (`/`) on the opening tag
instead of an end tag: `` instead of `` (`boolean`,
default: `false`).
See `tightSelfClosing` to control whether a space is used before the slash.
Not used in the HTML space.
###### `closeSelfClosing`
Close self-closing nodes with an extra slash (`/`): `` instead of
`` (`boolean`, default: `false`).
See `tightSelfClosing` to control whether a space is used before the slash.
Not used in the SVG space.
###### `collapseEmptyAttributes`
Collapse empty attributes: get `class` instead of `class=""` (`boolean`,
default: `false`).
Not used in the SVG space.
> 👉 **Note**: boolean attributes (such as `hidden`) are always collapsed.
###### `omitOptionalTags`
Omit optional opening and closing tags (`boolean`, default: `false`).
For example, in `
one
two
`, both `` 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.
###### `preferUnquoted`
Leave attributes unquoted if that results in less bytes (`boolean`, default:
`false`).
Not used in the SVG space.
###### `quote`
Preferred quote to use ([`Quote`][api-quote], default: `'"'`).
###### `quoteSmart`
Use the other quote if that results in less bytes (`boolean`, default: `false`).
###### `space`
Which space the document is in ([`Space`][api-space], default: `'html'`).
When an `