unist-util-select

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[unist][] utility with equivalents for querySelector, querySelectorAll,
and matches.

Contents

* What is this?
* When should I use this?
* Install
* Use
* API
* matches(selector, node)
* select(selector, tree)
* selectAll(selector, tree)
* Support
* Types
* Compatibility
* Related
* Contribute
* License

What is this?

This package lets you find nodes in a tree, similar to how querySelector,
querySelectorAll, and matches work with the DOM.

One notable difference between DOM and hast is that DOM nodes have references
to their parents, meaning that document.body.matches(':last-child') can
be evaluated to check whether the body is the last child of its parent.
This information is not stored in hast, so selectors like that don’t work.

When should I use this?

This utility works on any unist syntax tree and you can select all node types.
If you are working with [hast][], and only want to select elements, use
[hast-util-select][hast-util-select] instead.

This is a small utility that is quite useful, but is rather slow if you use it a
lot.
For each call, it has to walk the entire tree.
In some cases, walking the tree once with [unist-util-visit][unist-util-visit]
is smarter, such as when you want to change certain nodes.
On the other hand, this is quite powerful and fast enough for many other cases.

Install

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

``sh
npm install unist-util-select
`

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

`js
import {matches, select, selectAll} from "https://esm.sh/unist-util-select@5"
`

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

`html

`

Use

`js
import {u} from 'unist-builder'
import {matches, select, selectAll} from 'unist-util-select'

const tree = u('blockquote', [
u('paragraph', [u('text', 'Alpha')]),
u('paragraph', [u('text', 'Bravo')]),
u('code', 'Charlie'),
u('paragraph', [u('text', 'Delta')]),
u('paragraph', [u('text', 'Echo')]),
u('paragraph', [u('text', 'Foxtrot')]),
u('paragraph', [u('text', 'Golf')])
])

console.log(matches('blockquote, list', tree)) // => true

console.log(select('code ~ :nth-child(even)', tree))
// The paragraph with Delta

console.log(selectAll('code ~ :nth-child(even)', tree))
// The paragraphs with Delta and Foxtrot
`

API

This package exports the identifiers [matches][api-matches],
[select][api-select], and [selectAll][api-select-all].
There is no default export.

$3

Check that the given node matches selector.

This only checks the node itself, not the surrounding tree.
Thus, nesting in selectors is not supported (paragraph strong,
paragraph > strong), neither are selectors like :first-child, etc.
This only checks that the given node matches the selector.

###### Parameters

* selector (string)
— CSS selector, such as (heading, link, linkReference).
* node ([Node][node], optional)
— node that might match selector

###### Returns

Whether node matches selector (boolean).

###### Example

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

matches('strong, em', u('strong', [u('text', 'important')])) // => true
matches('[lang]', u('code', {lang: 'js'}, 'console.log(1)')) // => true
`

$3

Select the first node that matches selector in the given tree.

Searches the tree in [preorder][].

###### Parameters

* selector (string)
— CSS selector, such as (heading, link, linkReference).
* tree ([Node][node], optional)
— tree to search

###### Returns

First node in tree that matches selector or undefined if nothing is found.

This could be tree itself.

###### Example

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

console.log(
select(
'code ~ :nth-child(even)',
u('blockquote', [
u('paragraph', [u('text', 'Alpha')]),
u('paragraph', [u('text', 'Bravo')]),
u('code', 'Charlie'),
u('paragraph', [u('text', 'Delta')]),
u('paragraph', [u('text', 'Echo')])
])
)
)
`

Yields:

`js
{type: 'paragraph', children: [{type: 'text', value: 'Delta'}]}
`

$3

Select all nodes that match selector in the given tree.

Searches the tree in [preorder][].

###### Parameters

* selector (string)
— CSS selector, such as (heading, link, linkReference).
* tree ([Node][node], optional)
— tree to search

###### Returns

Nodes in tree that match selector.

This could include tree itself.

###### Example

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

console.log(
selectAll(
'code ~ :nth-child(even)',
u('blockquote', [
u('paragraph', [u('text', 'Alpha')]),
u('paragraph', [u('text', 'Bravo')]),
u('code', 'Charlie'),
u('paragraph', [u('text', 'Delta')]),
u('paragraph', [u('text', 'Echo')]),
u('paragraph', [u('text', 'Foxtrot')]),
u('paragraph', [u('text', 'Golf')])
])
)
)
`

Yields:

`js
[
{type: 'paragraph', children: [{type: 'text', value: 'Delta'}]},
{type: 'paragraph', children: [{type: 'text', value: 'Foxtrot'}]}
]
`

Support

[x] (universal selector)
* [x] , (multiple selector)
* [x] paragraph (type selector)
* [x] blockquote paragraph (combinator: descendant selector)
* [x] blockquote > paragraph (combinator: child selector)
* [x] code + paragraph (combinator: adjacent sibling selector)
* [x] code ~ paragraph (combinator: general sibling selector)
* [x] [attr] (attribute existence, checks that the value on the tree is not
nullish)
* [x] [attr=value] (attribute equality, this stringifies values on the tree)
* [x] [attr^=value] (attribute begins with, only works on strings)
* [x] [attr$=value] (attribute ends with, only works on strings)
[x] [attr=value] (attribute contains, only works on strings)
* [x] [attr~=value] (attribute contains, checks if value is in the array,
if there’s an array on the tree, otherwise same as attribute equality)
* [x] :is() (functional pseudo-class)
* [x] :has() (functional pseudo-class; also supports a:has(> b))
* [x] :not() (functional pseudo-class)
* [x] :blank (pseudo-class, blank and empty are the same: a parent without
children, or a node without value)
* [x] :empty (pseudo-class, blank and empty are the same: a parent without
children, or a node without value)
* [x] :root (pseudo-class, matches the given node)
* [x] :scope (pseudo-class, matches the given node)
[x] \ :first-child (pseudo-class)
[x] \ :first-of-type (pseudo-class)
[x] \ :last-child (pseudo-class)
[x] \ :last-of-type (pseudo-class)
[x] \ :only-child (pseudo-class)
[x] \ :only-of-type (pseudo-class)
[x] \ :nth-child() (functional pseudo-class)
[x] \ :nth-last-child() (functional pseudo-class)
[x] \ :nth-last-of-type() (functional pseudo-class)
[x] \ :nth-of-type() (functional pseudo-class)

###### Notes

\ — not supported in matches
* :any() and :matches() are renamed to :is() in CSS

Types

This package is fully typed with [TypeScript][].
It exports no additional types.

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-select@^5,
compatible with Node.js 16.

Related

* unist-util-is
— check if a node passes a test
* unist-util-visit
— recursively walk over nodes
* unist-util-visit-parents
— like visit, but with a stack of parents
* unist-builder
— create unist trees

Contribute

See [contributing.md][contributing] in [syntax-tree/.github][health] for
ways to get started.
See [support.md`][help] 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-select/workflows/main/badge.svg

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

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

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

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[collective]: https://opencollective.com/unified

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[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/main/contributing.md

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

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

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

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

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

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

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

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

[api-matches]: #matchesselector-node

[api-select]: #selectselector-tree

[api-select-all]: #selectallselector-tree