unist-util-is

unist utility to check if a node passes a test

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unist-util-is
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unist utility to check if nodes pass a test.

Contents

*   [`is(node[, test[, index, parent[, context]]])`](#isnode-test-index-parent-context)
*   [`convert(test)`](#converttest)
*   [`Check`](#check)
*   [`Test`](#test)
*   [`TestFunction`](#testfunction)
*   [Example of `convert`](#example-of-convert)

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-elementhast-util-is-element, works on hast elements.
For more advanced tests, unist-util-selectunist-util-select can be used to match against CSS selectors.

Install

This package is ESM onlyesm. In Node.js (version 16+), install with npm:
npm install unist-util-is

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

In browsers with esm.shesmsh:
<script type="module">
  import {is} from 'https://esm.sh/unist-util-is@6?bundle'
</script>

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 convertapi-convert and isapi-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]
— a test for a specific element
  • index (number, optional)
— the node’s position in its parent
— the node’s parent
  • context (unknown, optional)
— context object (`this`) to call `test` with
Returns
Whether node is a Nodenode 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
— a test for a specific node
Returns
A check (Checkapi-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
— 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<Record<string, unknown> | TestFunction | string>
  | Record<string, unknown>
  | 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 TestFunctionapi-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
— a node
  • index (number or undefined)
— the node’s position in its parent
— 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 Checkapi-check, Testapi-test, TestFunctionapi-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

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

Contribute

See contributing.mdcontributing in syntax-tree/.githubhealth for ways to get started. See support.mdsupport for ways to get help.
This project has a code of conductcoc. By interacting with this repository, organization, or community you agree to abide by its terms.

License

MITlicense © Titus Wormerauthor