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https://github.com/syntax-tree/hast-util-truncate

utility to truncate the tree to a certain number of characters
https://github.com/syntax-tree/hast-util-truncate

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utility to truncate the tree to a certain number of characters

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# hast-util-truncate



[![Build][build-badge]][build]

[![Coverage][coverage-badge]][coverage]

[![Downloads][downloads-badge]][downloads]

[![Size][size-badge]][size]

[![Sponsors][sponsors-badge]][collective]

[![Backers][backers-badge]][collective]

[![Chat][chat-badge]][chat]



[hast][] utility to truncate the tree to a certain number of characters.



## Contents



*   [What is this?](#what-is-this)

*   [When should I use this?](#when-should-i-use-this)

*   [Install](#install)

*   [Use](#use)

*   [API](#api)

    *   [`truncate(tree[, options])`](#truncatetree-options)

    *   [`Options`](#options)

*   [Types](#types)

*   [Compatibility](#compatibility)

*   [Security](#security)

*   [Related](#related)

*   [Contribute](#contribute)

*   [License](#license)



## What is this?



This package is a utility that takes a [hast][] (HTML) syntax tree and truncates

it to a certain number of characters, while otherwise preserving the tree

structure.



## When should I use this?



This is a small utility useful when you need to create a shorter version of a

potentially long document.



This utility is similar to [`hast-util-excerpt`][hast-util-excerpt], which

truncates a tree to a certain comment.



The rehype plugin

[`rehype-infer-description-meta`][rehype-infer-description-meta]

wraps both this utility and `hast-util-excerpt` to figure out a description of a

document, for use with [`rehype-meta`][rehype-meta].



## Install



This package is [ESM only][esm].

In Node.js (version 16+), install with [npm][]:



```sh

npm install hast-util-truncate

```



In Deno with [`esm.sh`][esmsh]:



```js

import {truncate} from 'https://esm.sh/hast-util-truncate@2'

```



In browsers with [`esm.sh`][esmsh]:



```html



  import {truncate} from 'https://esm.sh/hast-util-truncate@2?bundle'



```



## Use



Say our module `example.js` looks as follows:



```js

import {h} from 'hastscript'

import {truncate} from 'hast-util-truncate'



const tree = h('p', [

  'Lorem ipsum dolor sit amet, ',

  h('em', 'consectetur'),

  'adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud'

])



console.log(truncate(tree, {ellipsis: '…'}));

```



…now running `node example.js` yields:



```js

{

  type: 'element',

  tagName: 'p',

  properties: {},

  children: [

    {type: 'text', value: 'Lorem ipsum dolor sit amet, '},

    {

      type: 'element',

      tagName: 'em',

      properties: {},

      children: [{type: 'text', value: 'consectetur'}]

    },

    {

      type: 'text',

      value: 'adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim…'

    }

  ]

}

```



## API



This package exports the identifier [`truncate`][api-truncate].

There is no default export.



### `truncate(tree[, options])`



Truncate the tree to a certain number of characters.



###### Parameters



*   `tree` ([`Node`][node])

    — tree to truncate

*   `options` ([`Options`][api-options], optional)

    — configuration



###### Returns



Truncated copy of `tree` ([`Node`][node]).



### `Options`



Configuration (TypeScript type).



##### Fields



###### `options.size`



Number of characters to truncate to (`number`, default: `140`).



###### `options.ellipsis`



Value to use at truncation point (`string`, optional).



###### `options.maxCharacterStrip`



How far to walk back (`number`, default: `30`).

The algorithm attempts to break right after a word rather than the exact `size`.

Take for example the `|`, which is the actual break defined by `size`, and the

`…` is the location where the ellipsis is placed: `This… an|d that`.

Breaking at `|` would at best look bad but could likely result in things such as

`ass…` for `assignment`, which is not ideal.

`maxCharacterStrip` defines how far back the algorithm will walk to find a

pretty word break.

This prevents a potential slow operation on larger `size`s without any

whitespace.

If `maxCharacterStrip` characters are walked back and no nice break point is

found, the bad break point is used.

Set `maxCharacterStrip: 0` to not find a nice break.



###### `options.ignore`



Nodes to exclude from the resulting tree (`Array`).

These are not counted towards `size`.



## Types



This package is fully typed with [TypeScript][].

It exports the additional type [`Options`][api-options].



## 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-truncate@^2`,

compatible with Node.js 16.



## Security



Use of `hast-util-truncate` should be safe if the tree is already safe and

you’re not using user content in options.

When in doubt, use [`hast-util-sanitize`][hast-util-sanitize].



## Related



*   [`hast-util-excerpt`][hast-util-excerpt]

    — truncate the tree to a comment

*   [`rehype-infer-description-meta`][rehype-infer-description-meta]

    — infer file metadata from the contents of the document

*   [`rehype-meta`][rehype-meta]

    — add metadata to the head of a document



## Contribute



See [`contributing.md`][contributing] in [`syntax-tree/.github`][health] 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-truncate/workflows/main/badge.svg



[build]: https://github.com/syntax-tree/hast-util-truncate/actions



[coverage-badge]: https://img.shields.io/codecov/c/github/syntax-tree/hast-util-truncate.svg



[coverage]: https://codecov.io/github/syntax-tree/hast-util-truncate



[downloads-badge]: https://img.shields.io/npm/dm/hast-util-truncate.svg



[downloads]: https://www.npmjs.com/package/hast-util-truncate



[size-badge]: https://img.shields.io/badge/dynamic/json?label=minzipped%20size&query=$.size.compressedSize&url=https://deno.bundlejs.com/?q=hast-util-truncate



[size]: https://bundlejs.com/?q=hast-util-truncate



[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



[npm]: https://docs.npmjs.com/cli/install



[esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c



[esmsh]: https://esm.sh



[typescript]: https://www.typescriptlang.org



[license]: license



[author]: https://wooorm.com



[health]: https://github.com/syntax-tree/.github



[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/syntax-tree/hast



[node]: https://github.com/syntax-tree/hast#nodes



[hast-util-sanitize]: https://github.com/syntax-tree/hast-util-sanitize



[hast-util-excerpt]: https://github.com/syntax-tree/hast-util-excerpt



[rehype-infer-description-meta]: https://github.com/rehypejs/rehype-infer-description-meta



[rehype-meta]: https://github.com/rehypejs/rehype-meta



[api-truncate]: #truncatetree-options



[api-options]: #options