unist-util-select

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

What is this?
When should I use this?
Install
Use
API
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 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 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. In Node.js (version 16+), install with npm:

npm install unist-util-select

In Deno with esm.sh:

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

In browsers with esm.sh:

<script type="module">
  import {matches, select, selectAll} from "https://esm.sh/unist-util-select@5?bundle"
</script>

Use

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, select, and selectAll. There is no default export.

`matches(selector, node)`

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, optional) — node that might match selector

Returns

Whether node matches selector (boolean).

Example

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

`select(selector, tree)`

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, optional) — tree to search

Returns

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

This could be tree itself.

Example

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:

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

`selectAll(selector, tree)`

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, optional) — tree to search

Returns

Nodes in tree that match selector.

This could include tree itself.

Example

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:

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

Support

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

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 in syntax-tree/.github for ways to get started. See support.md for ways to get help.

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

Package detail