unist-util-is

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[unist][] utility to check if nodes pass a test.

Contents

* What is this? * When should I use this? * Install * Use * API * is(node[, test[, index, parent[, context]]]) * convert(test) * Check * Test * TestFunction * Examples * Example of convert * Types * Compatibility * Related * Contribute * License

What is this?

This package is a small utility that checks that a node is a certain node.

When should I use this?

Use this small utility if you find yourself repeating code for checking what nodes are.

A similar package, [hast-util-is-element][hast-util-is-element], works on hast elements.

For more advanced tests, [unist-util-select][unist-util-select] can be used to match against CSS selectors.

Install

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

npm install unist-util-is

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

import {is} from 'https://esm.sh/unist-util-is@6'

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

Use

import {is} from 'unist-util-is'
const node = {type: 'strong'}
const parent = {type: 'paragraph', children: [node]}
is() // => false
is({children: []}) // => false
is(node) // => true
is(node, 'strong') // => true
is(node, 'emphasis') // => false
is(node, node) // => true
is(parent, {type: 'paragraph'}) // => true
is(parent, {type: 'strong'}) // => false
is(node, test) // => false
is(node, test, 4, parent) // => false
is(node, test, 5, parent) // => true
function test(node, n) {
  return n === 5
}

API

This package exports the identifiers [convert][api-convert] and [is][api-is]. There is no default export.

is(node[, test[, index, parent[, context]]])

Check if node is a Node and whether it passes the given test.

###### Parameters

* node (unknown, optional) — thing to check, typically [Node][node] * test ([Test][api-test], optional) — a test for a specific element * index (number, optional) — the node’s position in its parent * parent ([Node][node], optional) — the node’s parent * context (unknown, optional) — context object (this) to call test with

###### Returns

Whether node is a [Node][node] and passes a test (boolean).

###### Throws

When an incorrect test, index, or parent is given. There is no error thrown when node is not a node.

convert(test)

Generate a check from a test.

Useful if you’re going to test many nodes, for example when creating a utility where something else passes a compatible test.

The created function is a bit faster because it expects valid input only: a node, index, and parent.

###### Parameters

* test ([Test][api-test], optional) — a test for a specific node

###### Returns

A check ([Check][api-check]).

Check

Check that an arbitrary value is a node (TypeScript type).

###### Parameters

* this (unknown, optional) — context object (this) to call test with * node (unknown) — anything (typically a node) * index (number, optional) — the node’s position in its parent * parent ([Node][node], optional) — the node’s parent

###### Returns

Whether this is a node and passes a test (boolean).

Test

Check for an arbitrary node (TypeScript type).

###### Type

type Test =
  | Array | TestFunction | string>
  | Record
  | TestFunction
  | string
  | null
  | undefined

Checks that the given thing is a node, and then:

* when string, checks that the node has that tag name * when function, see [TestFunction][api-test-function] * when object, checks that all keys in test are in node, and that they have (strictly) equal values * when Array, checks if one of the subtests pass

TestFunction

Check if a node passes a test (TypeScript type).

###### Parameters

* node ([Node][node]) — a node * index (number or undefined) — the node’s position in its parent * parent ([Node][node] or undefined) — the node’s parent

###### Returns

Whether this node passes the test (boolean, optional).

Examples

Example of convert

import {u} from 'unist-builder'
import {convert} from 'unist-util-is'
const test = convert('leaf')
const tree = u('tree', [
  u('node', [u('leaf', '1')]),
  u('leaf', '2'),
  u('node', [u('leaf', '3'), u('leaf', '4')]),
  u('leaf', '5')
])
const leafs = tree.children.filter(function (child, index) {
  return test(child, index, tree)
})
console.log(leafs)

Yields:

[{type: 'leaf', value: '2'}, {type: 'leaf', value: '5'}]

Types

This package is fully typed with [TypeScript][]. It exports the additional types [Check][api-check], [Test][api-test], [TestFunction][api-test-function].

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-is@^6, compatible with Node.js 16.

Related

* unist-util-find-after — find a node after another node * unist-util-find-before — find a node before another node * unist-util-find-all-after — find all nodes after another node * unist-util-find-all-before — find all nodes before another node * unist-util-find-all-between — find all nodes between two nodes * unist-util-filter — create a new tree with nodes that pass a check * unist-util-remove — remove nodes from tree

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] © [Titus Wormer][author]

[api-check]: #check

[api-convert]: #converttest

[api-is]: #isnode-test-index-parent-context

[api-test]: #test

[api-test-function]: #testfunction

[author]: https://wooorm.com

[backers-badge]: https://opencollective.com/unified/backers/badge.svg

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

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

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

[chat-badge]: https://img.shields.io/badge/chat-discussions-success.svg

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

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

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

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

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

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

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

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

[esmsh]: https://esm.sh

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

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

[license]: license

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

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

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

[size-badge]: https://img.shields.io/badge/dynamic/json?label=minzipped%20size&query=$.size.compressedSize&url=https://deno.bundlejs.com/?q=unist-util-is

[sponsors-badge]: https://opencollective.com/unified/sponsors/badge.svg

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

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

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

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