# hast-util-format
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[hast][] utility to format whitespace in HTML.
## Contents
* [What is this?](#what-is-this)
* [When should I use this?](#when-should-i-use-this)
* [Install](#install)
* [Use](#use)
* [API](#api)
* [`Options`](#options)
* [`format(tree, options)`](#formattree-options)
* [Compatibility](#compatibility)
* [Related](#related)
* [Security](#security)
* [Contribute](#contribute)
* [License](#license)
## What is this?
This package is a utility that formats whitespace in HTML.
In short, it works as follows:
* collapse all existing whitespace to either a line ending or a single space
([`hast-util-minify-whitespace`][hast-util-minify-whitespace])
* remove those spaces and line endings if they do not contribute to the
document
* inject needed line endings
* indent previously collapsed line endings properly
## When should I use this?
This package is useful when you want to improve the readability of an HTML
fragment as it adds insignificant but pretty whitespace between elements.
The plugin [`rehype-format`][rehype-format] uses this package to format HTML
at the plugin level.
The package [`hast-util-minify-whitespace`][hast-util-minify-whitespace] does
the inverse.
## Install
This package is [ESM only][esm].
In Node.js (version 16+), install with [npm][]:
```sh
npm install hast-util-format
```
In Deno with [`esm.sh`][esmsh]:
```js
import {format} from 'https://esm.sh/hast-util-format@1'
```
In browsers with [`esm.sh`][esmsh]:
```html
```
## Use
Say we have the following `example.html`:
```html
Hello!
```
Say we have the following `example.js`:
```js
import fs from 'node:fs/promises'
import {format} from 'hast-util-format'
import {fromHtml} from 'hast-util-from-html'
import {toHtml} from 'hast-util-to-html'
const document = await fs.readFile('example.html', 'utf8')
const tree = fromHtml(document)
format(tree)
const result = toHtml(tree)
console.log(result)
```
…now running `node example.js` yields:
```html
Hello!
```
> 👉 **Note**:
> some of the changes have been made by `hast-util-to-html`.
## API
### `Options`
Configuration.
###### Fields
* `blanks?` (`Array | null | undefined`)
— list of tag names to join with a blank line (default: `[]`);
these tags,
when next to each other,
are joined by a blank line (`\n\n`);
for example,
when `['head', 'body']` is given,
a blank line is added between these two
* `indent?` (`string | number | null | undefined`)
— indentation per level (default: `2`);
when `number`,
uses that amount of spaces; when `string`,
uses that per indentation level
* `indentInitial?` (`boolean | null | undefined`)
— whether to indent the first level (default: `true`);
this is usually the ``,
thus not indenting `head` and `body`
### `format(tree, options)`
Format whitespace in HTML.
###### Parameters
* `tree` (`Root`)
— tree
* `options?` (`Options | null | undefined`)
— configuration (optional)
###### Returns
Nothing (`undefined`).
## 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-format@1`,
compatible with Node.js 16.
## Related
* [`hast-util-minify-whitespace`][hast-util-minify-whitespace]
— minify whitespace between elements
## Security
This package is safe.
## Contribute
See [`contributing.md` in `syntax-tree/.github`][contributing] for ways to get
started.
See [`support.md`][support] for ways to get help.
This project has a [code of conduct][coc].
By interacting with this repository, organization, or community you agree to
abide by its terms.
## License
[MIT][license] © [Titus Wormer][author]
[build-badge]: https://github.com/syntax-tree/hast-util-format/workflows/main/badge.svg
[build]: https://github.com/syntax-tree/hast-util-format/actions
[coverage-badge]: https://img.shields.io/codecov/c/github/syntax-tree/hast-util-format.svg
[coverage]: https://codecov.io/github/syntax-tree/hast-util-format
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[downloads]: https://www.npmjs.com/package/hast-util-format
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[size]: https://bundlejs.com/?q=hast-util-format
[sponsors-badge]: https://opencollective.com/unified/sponsors/badge.svg
[backers-badge]: https://opencollective.com/unified/backers/badge.svg
[collective]: https://opencollective.com/unified
[chat-badge]: https://img.shields.io/badge/chat-discussions-success.svg
[chat]: https://github.com/syntax-tree/unist/discussions
[esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c
[npm]: https://docs.npmjs.com/cli/install
[esmsh]: https://esm.sh
[license]: license
[author]: https://wooorm.com
[contributing]: https://github.com/syntax-tree/.github/blob/main/contributing.md
[support]: https://github.com/syntax-tree/.github/blob/main/support.md
[coc]: https://github.com/syntax-tree/.github/blob/main/code-of-conduct.md
[hast]: https://github.com/hast/hast
[hast-util-minify-whitespace]: https://github.com/rehypejs/rehype-minify/tree/main/packages/hast-util-minify-whitespace
[rehype-format]: https://github.com/rehypejs/rehype-format