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🎉 initiate project *astro_rewrite*
2023-07-19 21:31:30 +02:00
# unist-util-is
[![Build][build-badge]][build]
[![Coverage][coverage-badge]][coverage]
[![Downloads][downloads-badge]][downloads]
[![Size][size-badge]][size]
[![Sponsors][sponsors-badge]][collective]
[![Backers][backers-badge]][collective]
[![Chat][chat-badge]][chat]
[unist][] utility to check if nodes pass a test.
## Contents
* [What is this?](#what-is-this)
* [When should I use this?](#when-should-i-use-this)
* [Install](#install)
* [Use](#use)
* [API](#api)
* [`is(node[, test[, index, parent[, context]]])`](#isnode-test-index-parent-context)
* [`convert(test)`](#converttest)
* [`AssertAnything`](#assertanything)
* [`AssertPredicate`](#assertpredicate)
* [`Test`](#test)
* [`TestFunctionAnything`](#testfunctionanything)
* [`PredicateTest`](#predicatetest)
* [`TestFunctionPredicate`](#testfunctionpredicate)
* [Examples](#examples)
* [Example of `convert`](#example-of-convert)
* [Types](#types)
* [Compatibility](#compatibility)
* [Related](#related)
* [Contribute](#contribute)
* [License](#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 14.14+ and 16.0+), install with [npm][]:
```sh
npm install unist-util-is
```
In Deno with [`esm.sh`][esmsh]:
```js
import {is} from 'https://esm.sh/unist-util-is@5'
```
In browsers with [`esm.sh`][esmsh]:
```html
<script type="module">
import {is} from 'https://esm.sh/unist-util-is@5?bundle'
</script>
```
## Use
```js
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`][convert] and [`is`][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`)
— thing to check, typically [`Node`][node]
* `test` ([`Test`][test] or [`PredicateTest`][predicatetest], optional)
— a check for a specific element
* `index` (`number`, optional)
— the node’s position in its parent
* `parent` ([`Node`][node], optional)
— the node’s parent
* `context` (`any`, 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`][test] or [`PredicateTest`][predicatetest], optional)
— a check for a specific node
###### Returns
An assertion ([`AssertAnything`][assertanything] or
[`AssertPredicate`][assertpredicate]).
### `AssertAnything`
Check that an arbitrary value is a node, unaware of TypeScript inferral
(TypeScript type).
###### Parameters
* `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`).
### `AssertPredicate`
Check that an arbitrary value is a specific node, aware of TypeScript
(TypeScript type).
###### Type parameters
* `Kind` ([`Node`][node])
— node type
###### Parameters
* `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 (`node is Kind`).
### `Test`
Check for an arbitrary node, unaware of TypeScript inferral (TypeScript
type).
###### Type
```ts
type Test =
| null
| undefined
| string
| Record<string, unknown>
| TestFunctionAnything
| Array<string | Record<string, unknown> | TestFunctionAnything>
```
Checks that the given thing is a node, and then:
* when `string`, checks that the node has that tag name
* when `function`, see [`TestFunctionAnything`][testfunctionanything]
* 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
### `TestFunctionAnything`
Check if a node passes a test, unaware of TypeScript inferral (TypeScript
type).
###### Parameters
* `node` ([`Node`][node])
— a node
* `index` (`number`, optional)
— the node’s position in its parent
* `parent` ([`Node`][node], optional)
— the node’s parent
###### Returns
Whether this node passes the test (`boolean`).
### `PredicateTest`
Check for a node that can be inferred by TypeScript (TypeScript type).
###### Type
```ts
type PredicateTest<Kind extends Node> =
| Kind['type']
| Partial<Kind>
| TestFunctionPredicate<Kind>
| Array<Kind['type'] | Partial<Kind> | TestFunctionPredicate<Kind>>
```
See [`TestFunctionPredicate`][testfunctionpredicate].
### `TestFunctionPredicate`
Check if a node passes a certain node test (TypeScript type).
###### Type parameters
* `Kind` ([`Node`][node])
— node type
###### Parameters
* `node` ([`Node`][node])
— a node
* `index` (`number`, optional)
— the node’s position in its parent
* `parent` ([`Node`][node], optional)
— the node’s parent
###### Returns
Whether this node passes the test (`node is Kind`).
## Examples
### Example of `convert`
```js
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((child, index) => test(child, index, tree))
console.log(leafs)
```
Yields:
```js
[{type: 'leaf', value: '2'}, {type: 'leaf', value: '5'}]
```
## Types
This package is fully typed with [TypeScript][].
It exports the additional types [`AssertAnything`][assertanything],
[`AssertPredicate`][assertpredicate], [`Test`][test],
[`TestFunctionAnything`][testfunctionanything],
[`TestFunctionPredicate`][testfunctionpredicate], and
[`PredicateTest`][predicatetest].
## Compatibility
Projects maintained by the unified collective are compatible with all maintained
versions of Node.js.
As of now, that is Node.js 14.14+ and 16.0+.
Our projects sometimes work with older versions, but this is not guaranteed.
## Related
* [`unist-util-find-after`](https://github.com/syntax-tree/unist-util-find-after)
— find a node after another node
* [`unist-util-find-before`](https://github.com/syntax-tree/unist-util-find-before)
— find a node before another node
* [`unist-util-find-all-after`](https://github.com/syntax-tree/unist-util-find-all-after)
— find all nodes after another node
* [`unist-util-find-all-before`](https://github.com/syntax-tree/unist-util-find-all-before)
— find all nodes before another node
* [`unist-util-find-all-between`](https://github.com/mrzmmr/unist-util-find-all-between)
— find all nodes between two nodes
* [`unist-util-filter`](https://github.com/syntax-tree/unist-util-filter)
— create a new tree with nodes that pass a check
* [`unist-util-remove`](https://github.com/syntax-tree/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]
<!-- Definitions -->
[build-badge]: https://github.com/syntax-tree/unist-util-is/workflows/main/badge.svg
[build]: https://github.com/syntax-tree/unist-util-is/actions
[coverage-badge]: https://img.shields.io/codecov/c/github/syntax-tree/unist-util-is.svg
[coverage]: https://codecov.io/github/syntax-tree/unist-util-is
[downloads-badge]: https://img.shields.io/npm/dm/unist-util-is.svg
[downloads]: https://www.npmjs.com/package/unist-util-is
[size-badge]: https://img.shields.io/bundlephobia/minzip/unist-util-is.svg
[size]: https://bundlephobia.com/result?p=unist-util-is
[sponsors-badge]: https://opencollective.com/unified/sponsors/badge.svg
[backers-badge]: https://opencollective.com/unified/backers/badge.svg
[collective]: https://opencollective.com/unified
[chat-badge]: https://img.shields.io/badge/chat-discussions-success.svg
[chat]: https://github.com/syntax-tree/unist/discussions
[npm]: https://docs.npmjs.com/cli/install
[esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c
[esmsh]: https://esm.sh
[typescript]: https://www.typescriptlang.org
[license]: license
[author]: https://wooorm.com
[health]: https://github.com/syntax-tree/.github
[contributing]: https://github.com/syntax-tree/.github/blob/main/contributing.md
[support]: https://github.com/syntax-tree/.github/blob/main/support.md
[coc]: https://github.com/syntax-tree/.github/blob/main/code-of-conduct.md
[unist]: https://github.com/syntax-tree/unist
[node]: https://github.com/syntax-tree/unist#node
[hast-util-is-element]: https://github.com/syntax-tree/hast-util-is-element
[unist-util-select]: https://github.com/syntax-tree/unist-util-select
[is]: #isnode-test-index-parent-context
[convert]: #converttest
[assertanything]: #assertanything
[assertpredicate]: #assertpredicate
[test]: #test
[testfunctionanything]: #testfunctionanything
[testfunctionpredicate]: #testfunctionpredicate
[predicatetest]: #predicatetest
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