unist-util-select

What is unist-util-select?

The unist-util-select package is a utility for selecting nodes in a Unist syntax tree using CSS-like selectors. It allows for querying and manipulating nodes in a tree structure, making it easier to work with abstract syntax trees (ASTs) in JavaScript.

What are unist-util-select's main functionalities?

Select a single node

This feature allows you to select a single node from the tree that matches the given selector. In this example, it selects the first 'paragraph' node in the tree.

const select = require('unist-util-select').select;
const tree = { type: 'root', children: [{ type: 'paragraph', children: [{ type: 'text', value: 'Hello, world!' }] }] };
const node = select('paragraph', tree);
console.log(node);

Select multiple nodes

This feature allows you to select all nodes from the tree that match the given selector. In this example, it selects all 'paragraph' nodes in the tree.

const selectAll = require('unist-util-select').selectAll;
const tree = { type: 'root', children: [{ type: 'paragraph', children: [{ type: 'text', value: 'Hello, world!' }] }, { type: 'paragraph', children: [{ type: 'text', value: 'Another paragraph.' }] }] };
const nodes = selectAll('paragraph', tree);
console.log(nodes);

Select nodes with specific attributes

This feature allows you to select nodes that have specific attributes. In this example, it selects all nodes with a 'data-id' attribute equal to 'intro'.

const selectAll = require('unist-util-select').selectAll;
const tree = { type: 'root', children: [{ type: 'paragraph', data: { id: 'intro' }, children: [{ type: 'text', value: 'Introduction' }] }, { type: 'paragraph', data: { id: 'main' }, children: [{ type: 'text', value: 'Main content' }] }] };
const nodes = selectAll('[data-id="intro"]', tree);
console.log(nodes);

Other packages similar to unist-util-select

unist-util-visit

unist-util-visit is a utility for recursively visiting nodes in a Unist syntax tree. It allows for more complex traversal and manipulation of nodes compared to unist-util-select, but does not use CSS-like selectors.

hast-util-select

hast-util-select is similar to unist-util-select but is specifically designed for working with HAST (Hypertext Abstract Syntax Tree) nodes. It provides CSS-like selectors for querying HAST nodes.

unist-builder

unist-builder is a utility for creating Unist syntax trees. While it does not provide querying capabilities like unist-util-select, it is useful for constructing trees programmatically.

README

unist-util-select

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 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

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

License

MIT © Eugene Sharygin