unist-util-filter

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[unist][] utility to create a new tree with only nodes that pass a test.

Contents

* What is this?
* When should I use this?
* Install
* Use
* API
* [filter(tree[, options][, test])](#filtertree-options-test)
* Options
* Types
* Compatibility
* Related
* Contribute
* License

What is this?

This is a small utility that helps you clean a tree.

When should I use this?

You can use this utility to remove things from a tree.
This utility is very similar to [unist-util-remove][unist-util-remove], which
changes the given tree.
Modifying a tree like that utility does is much faster on larger documents.

You can also walk the tree with [unist-util-visit][unist-util-visit] to remove
nodes.
To create trees, use [unist-builder][unist-builder].

Install

This package is [ESM only][esm].
In Node.js (version 16+), install with [npm][]:

``sh
npm install unist-util-filter
`

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

`js
import {filter} from 'https://esm.sh/unist-util-filter@5'
`

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

`html

`

Use

`js
import {u} from 'unist-builder'
import {filter} from 'unist-util-filter'

const tree = u('root', [
u('leaf', '1'),
u('parent', [u('leaf', '2'), u('parent', [u('leaf', '3')])]),
u('leaf', '4')
])

const newTree = filter(tree, node => node.type !== 'leaf' || node.value % 2 === 0)

console.dir(newTree, {depth: null})
`

Yields:

`js
{
type: 'root',
children: [
{type: 'parent', children: [{type: 'leaf', value: '2'}]},
{type: 'leaf', value: '4'}
]
}
`

API

This package exports the identifier [filter][filter].
There is no default export.

$3

Create a new tree of copies of all nodes that pass test.

The tree is walked in [preorder][] (NLR), visiting the node itself, then its
head, etc.

###### Parameters

* tree ([Node][node])
— tree to filter
* options ([Options][options], optional)
— configuration
* test ([Test][test], optional)
— unist-util-is compatible test

###### Returns

New filtered tree ([Node][node] or undefined).

undefined is returned if tree itself didn’t pass the test, or is cascaded
away.

$3

Configuration (TypeScript type).

###### Fields

* cascade (boolean, default: true)
— whether to drop parent nodes if they had children, but all their
children were filtered out

Types

This package is fully typed with [TypeScript][].
It exports the additional type [Options][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, unist-util-filter@^5,
compatible with Node.js 16.

Related

* unist-util-visit
— walk the tree
* unist-util-visit-parents
— walk the tree with a stack of parents
* unist-util-map
— create a new tree with all nodes mapped by a given function
* unist-util-flatmap
— create a new tree by mapping (to an array) by a given function
* unist-util-remove
— remove nodes from a tree that pass a test
* unist-util-select
— select nodes with CSS-like selectors

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] © Eugene Sharygin

[build-badge]: https://github.com/syntax-tree/unist-util-filter/workflows/main/badge.svg

[build]: https://github.com/syntax-tree/unist-util-filter/actions

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

[coverage]: https://codecov.io/github/syntax-tree/unist-util-filter

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

[downloads]: https://www.npmjs.com/package/unist-util-filter

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[size]: https://bundlejs.com/?q=unist-util-filter

[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

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

[contributing]: https://github.com/syntax-tree/.github/blob/HEAD/contributing.md

[support]: https://github.com/syntax-tree/.github/blob/HEAD/support.md

[coc]: https://github.com/syntax-tree/.github/blob/HEAD/code-of-conduct.md

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

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

[preorder]: https://www.geeksforgeeks.org/tree-traversals-inorder-preorder-and-postorder/

[unist-util-remove]: https://github.com/syntax-tree/unist-util-remove

[unist-util-visit]: https://github.com/syntax-tree/unist-util-visit

[unist-builder]: https://github.com/syntax-tree/unist-builder

[test]: https://github.com/syntax-tree/unist-util-is#test

[filter]: #filtertree-options-test

[options]: #options