hast-util-select

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[hast][github-hast] utility with equivalents for
matches, querySelector, and querySelectorAll.

Contents

* What is this?
* When should I use this?
* Install
* Use
* API
* [matches(selector, node[, space])](#matchesselector-node-space)
* [select(selector, tree[, space])](#selectselector-tree-space)
* [selectAll(selector, tree[, space])](#selectallselector-tree-space)
* Space
* Support
* Unsupported
* Types
* Compatibility
* Security
* Related
* Contribute
* License

What is this?

This package lets you find nodes in a tree,
similar to how matches,
querySelector,
and
querySelectorAll 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 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][github-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.

This utility is similar to
[unist-util-select][github-unist-util-select],
which can find and match any unist node.

Install

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

``sh
npm install hast-util-select
`

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

`js
import {matches, select, selectAll} from 'https://esm.sh/hast-util-select@6'
`

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

`html

`

Use

`js
import {h} from 'hastscript'
import {matches, select, selectAll} from 'hast-util-select'

const tree = h('section', [
h('p', 'Alpha'),
h('p', 'Bravo'),
h('h1', 'Charlie'),
h('p', 'Delta'),
h('p', 'Echo'),
h('p', 'Foxtrot'),
h('p', 'Golf')
])

console.log(matches('section', tree)) // true

console.log(select('h1 ~ :nth-child(even)', tree))
// The paragraph with Delta

console.log(selectAll('h1 ~ :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 element itself,
not the surrounding tree.
Thus,
nesting in selectors is not supported (p b, p > b),
neither are selectors like :first-child,
etc.
This only checks that the given element matches the selector.

###### Parameters

* selector
(string, example: 'h1', 'a, b')
— CSS selector
* node
([Node][github-hast-nodes], optional)
— node that might match selector,
should be an element
* space
([Space][api-space], default: 'html')
— name of namespace

###### Returns

Whether node matches selector (boolean).

###### Example

`js
import {h} from 'hastscript'
import {matches} from 'hast-util-select'

matches('b, i', h('b')) // => true
matches(':any-link', h('a')) // => false
matches(':any-link', h('a', {href: '#'})) // => true
matches('.classy', h('a', {className: ['classy']})) // => true
matches('#id', h('a', {id: 'id'})) // => true
matches('[lang|=en]', h('a', {lang: 'en'})) // => true
matches('[lang|=en]', h('a', {lang: 'en-GB'})) // => true
`

$3

Select the first element that matches selector in the given tree.
Searches the tree in [preorder][github-unist-preorder].

###### Parameters

* selector
(string, example: 'h1', 'a, b')
— CSS selector, such as (h1, a, b)
* tree
([Node][github-hast-nodes], optional)
— tree to search
* space
([Space][api-space], default: 'html')
— name of namespace

###### Returns

First element in tree that matches selector or undefined if nothing is
found.
This could be tree itself.

###### Example

`js
import {h} from 'hastscript'
import {select} from 'hast-util-select'

console.log(
select(
'h1 ~ :nth-child(even)',
h('section', [
h('p', 'Alpha'),
h('p', 'Bravo'),
h('h1', 'Charlie'),
h('p', 'Delta'),
h('p', 'Echo')
])
)
)
`

Yields:

`js
{ type: 'element',
tagName: 'p',
properties: {},
children: [ { type: 'text', value: 'Delta' } ] }
`

$3

Select all elements that match selector in the given tree.
Searches the tree in [preorder][github-unist-preorder].

###### Parameters

* selector
(string, example: 'h1', 'a, b')
— CSS selector
* tree
([Node][github-hast-nodes], optional)
— tree to search
* space
([Space][api-space], default: 'html')
— name of namespace

###### Returns

Elements in tree that match selector.
This could include tree itself.

###### Example

`js
import {h} from 'hastscript'
import {selectAll} from 'hast-util-select'

console.log(
selectAll(
'h1 ~ :nth-child(even)',
h('section', [
h('p', 'Alpha'),
h('p', 'Bravo'),
h('h1', 'Charlie'),
h('p', 'Delta'),
h('p', 'Echo'),
h('p', 'Foxtrot'),
h('p', 'Golf')
])
)
)
`

Yields:

`js
[ { type: 'element',
tagName: 'p',
properties: {},
children: [ { type: 'text', value: 'Delta' } ] },
{ type: 'element',
tagName: 'p',
properties: {},
children: [ { type: 'text', value: 'Foxtrot' } ] } ]
`

$3

Namespace (TypeScript type).

###### Type

`ts
type Space = 'html' | 'svg'
`

Support

[x] (universal selector)
* [x] , (multiple selector)
* [x] p (type selector)
* [x] .class (class selector)
* [x] #id (id selector)
* [x] article p (combinator: descendant selector)
* [x] article > p (combinator: child selector)
* [x] h1 + p (combinator: next-sibling selector)
* [x] h1 ~ p (combinator: subsequent sibling selector)
* [x] [attr] (attribute existence)
* [x] [attr… i] (attribute case-insensitive)
* [x] [attr… s] (attribute case-sensitive) (useless, default)
* [x] [attr=value] (attribute equality)
* [x] [attr~=value] (attribute contains in space-separated list)
* [x] [attr|=value] (attribute equality or prefix)
* [x] [attr^=value] (attribute begins with)
* [x] [attr$=value] (attribute ends with)
[x] [attr=value] (attribute contains)
* [x] :dir() (functional pseudo-class)
* [x] :has() (functional pseudo-class; also supports a:has(> b))
* [x] :is() (functional pseudo-class)
* [x] :lang() (functional pseudo-class)
* [x] :not() (functional pseudo-class)
* [x] :any-link (pseudo-class)
* [x] :blank (pseudo-class)
* [x] :checked (pseudo-class)
* [x] :disabled (pseudo-class)
* [x] :empty (pseudo-class)
* [x] :enabled (pseudo-class)
* [x] :optional (pseudo-class)
* [x] :read-only (pseudo-class)
* [x] :read-write (pseudo-class)
* [x] :required (pseudo-class)
* [x] :root (pseudo-class)
* [x] :scope (pseudo-class):
[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)

Unsupported

* [ ] † || (column combinator)
* [ ] † ns|E (namespace type selector)
[ ] † |E (any namespace type selector)
* [ ] † |E (no namespace type selector)
* [ ] † [ns|attr] (namespace attribute)
[ ] † [|attr] (any namespace attribute)
* [ ] † [|attr] (no namespace attribute)
* [ ] ‖ :nth-child(n of S) (functional pseudo-class, note: scoping to
parents is not supported)
* [ ] ‖ :nth-last-child(n of S) (functional pseudo-class, note: scoping to
parents is not supported)
* [ ] † :active (pseudo-class)
* [ ] † :autofill (pseudo-class)
* [ ] † :buffering (pseudo-class)
* [ ] § :closed (pseudo-class)
* [ ] † :current (pseudo-class)
* [ ] † :current() (functional pseudo-class)
* [ ] † :default (pseudo-class)
* [ ] † :defined (pseudo-class)
* [ ] † :focus (pseudo-class)
* [ ] † :focus-visible (pseudo-class)
* [ ] † :focus-within (pseudo-class)
* [ ] † :fullscreen (pseudo-class)
* [ ] † :future (pseudo-class)
* [ ] § :host() (functional pseudo-class)
* [ ] § :host-context() (functional pseudo-class)
* [ ] † :hover (pseudo-class)
* [ ] ‡ :in-range (pseudo-class)
* [ ] † :indeterminate (pseudo-class)
* [ ] ‡ :invalid (pseudo-class)
* [ ] † :link (pseudo-class)
* [ ] † :local-link (pseudo-class)
* [ ] † :modal (pseudo-class)
* [ ] † :muted (pseudo-class)
* [ ] † :nth-col() (functional pseudo-class)
* [ ] † :nth-last-col() (functional pseudo-class)
* [ ] § :open (pseudo-class)
* [ ] ‡ :out-of-range (pseudo-class)
* [ ] † :past (pseudo-class)
* [ ] † :paused (pseudo-class)
* [ ] † :placeholder-shown (pseudo-class)
* [ ] † :playing (pseudo-class)
* [ ] † :seeking (pseudo-class)
* [ ] † :stalled (pseudo-class)
* [ ] † :target (pseudo-class)
* [ ] † :target-within (pseudo-class)
* [ ] † :user-invalid (pseudo-class)
* [ ] ‡ :valid (pseudo-class)
* [ ] † :visited (pseudo-class)
* [ ] † :volume-locked (pseudo-class)
* [ ] § :where() (functional pseudo-class)
* [ ] † ::before (pseudo-elements: none are supported)

###### Notes

\ — not supported in matches
* † — needs a user,
browser,
interactivity,
scripting,
or whole CSS to make sense
* ‡ — not very interested in writing / including the code for this
* § — too new,
the spec is still changing
* ‖ — pr wanted!
* :any() and :matches() are renamed to :is() in CSS.

Types

This package is fully typed with [TypeScript][].
It exports the additional type [Space][api-space].

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-select@6,
compatible with Node.js 16.

Security

This package does not change the syntax tree so there are no openings for
[cross-site scripting (XSS)][wikipedia-xss] attacks.

Related

* [unist-util-select][github-unist-util-select]
— select unist nodes with CSS-like selectors
* hast-util-find-and-replace
— find and replace text in a hast tree
* hast-util-parse-selector
— create an element from a simple CSS selector
* hast-util-from-selector
— create an element from a complex CSS selector

Contribute

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

This project has a [code of conduct][health-coc].
By interacting with this repository,
organization,
or community you agree to abide by its terms.

License

[MIT][file-license] © [Titus Wormer][wooorm]

[api-matches]: #matchesselector-node-space

[api-select]: #selectselector-tree-space

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

[api-space]: #space

[badge-build-image]: https://github.com/syntax-tree/hast-util-select/workflows/main/badge.svg

[badge-build-url]: https://github.com/syntax-tree/hast-util-select/actions

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

[badge-coverage-url]: https://codecov.io/github/syntax-tree/hast-util-select

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

[badge-downloads-url]: https://www.npmjs.com/package/hast-util-select

[badge-size-image]: https://img.shields.io/bundlejs/size/hast-util-select

[badge-size-url]: https://bundlejs.com/?q=hast-util-select

[esmsh]: https://esm.sh

[file-license]: license

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

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

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

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

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

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

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

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

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

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

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

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

[wikipedia-xss]: https://en.wikipedia.org/wiki/Cross-site_scripting

[wooorm]: https://wooorm.com