420 lines
10 KiB
Plaintext
420 lines
10 KiB
Plaintext
# unist-util-is
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[![Build][build-badge]][build]
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[![Coverage][coverage-badge]][coverage]
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[![Downloads][downloads-badge]][downloads]
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[![Size][size-badge]][size]
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[![Sponsors][sponsors-badge]][collective]
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[![Backers][backers-badge]][collective]
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[![Chat][chat-badge]][chat]
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[unist][] utility to check if nodes pass a test.
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## Contents
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* [What is this?](#what-is-this)
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* [When should I use this?](#when-should-i-use-this)
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* [Install](#install)
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* [Use](#use)
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* [API](#api)
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* [`is(node[, test[, index, parent[, context]]])`](#isnode-test-index-parent-context)
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* [`convert(test)`](#converttest)
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* [`AssertAnything`](#assertanything)
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* [`AssertPredicate`](#assertpredicate)
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* [`Test`](#test)
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* [`TestFunctionAnything`](#testfunctionanything)
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* [`PredicateTest`](#predicatetest)
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* [`TestFunctionPredicate`](#testfunctionpredicate)
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* [Examples](#examples)
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* [Example of `convert`](#example-of-convert)
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* [Types](#types)
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* [Compatibility](#compatibility)
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* [Related](#related)
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* [Contribute](#contribute)
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* [License](#license)
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## What is this?
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This package is a small utility that checks that a node is a certain node.
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## When should I use this?
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Use this small utility if you find yourself repeating code for checking what
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nodes are.
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A similar package, [`hast-util-is-element`][hast-util-is-element], works on hast
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elements.
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For more advanced tests, [`unist-util-select`][unist-util-select] can be used
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to match against CSS selectors.
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## Install
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This package is [ESM only][esm].
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In Node.js (version 14.14+ and 16.0+), install with [npm][]:
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```sh
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npm install unist-util-is
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```
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In Deno with [`esm.sh`][esmsh]:
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```js
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import {is} from 'https://esm.sh/unist-util-is@5'
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```
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In browsers with [`esm.sh`][esmsh]:
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```html
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<script type="module">
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import {is} from 'https://esm.sh/unist-util-is@5?bundle'
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</script>
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```
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## Use
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```js
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import {is} from 'unist-util-is'
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const node = {type: 'strong'}
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const parent = {type: 'paragraph', children: [node]}
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is() // => false
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is({children: []}) // => false
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is(node) // => true
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is(node, 'strong') // => true
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is(node, 'emphasis') // => false
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is(node, node) // => true
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is(parent, {type: 'paragraph'}) // => true
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is(parent, {type: 'strong'}) // => false
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is(node, test) // => false
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is(node, test, 4, parent) // => false
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is(node, test, 5, parent) // => true
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function test(node, n) {
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return n === 5
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}
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```
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## API
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This package exports the identifiers [`convert`][convert] and [`is`][is].
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There is no default export.
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### `is(node[, test[, index, parent[, context]]])`
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Check if `node` is a `Node` and whether it passes the given test.
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###### Parameters
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* `node` (`unknown`)
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— thing to check, typically [`Node`][node]
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* `test` ([`Test`][test] or [`PredicateTest`][predicatetest], optional)
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— a check for a specific element
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* `index` (`number`, optional)
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— the node’s position in its parent
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* `parent` ([`Node`][node], optional)
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— the node’s parent
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* `context` (`any`, optional)
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— context object (`this`) to call `test` with
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###### Returns
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Whether `node` is a [`Node`][node] and passes a test (`boolean`).
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###### Throws
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When an incorrect `test`, `index`, or `parent` is given.
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There is no error thrown when `node` is not a node.
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### `convert(test)`
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Generate a check from a test.
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Useful if you’re going to test many nodes, for example when creating a
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utility where something else passes a compatible test.
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The created function is a bit faster because it expects valid input only:
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a `node`, `index`, and `parent`.
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###### Parameters
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* `test` ([`Test`][test] or [`PredicateTest`][predicatetest], optional)
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— a check for a specific node
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###### Returns
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An assertion ([`AssertAnything`][assertanything] or
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[`AssertPredicate`][assertpredicate]).
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### `AssertAnything`
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Check that an arbitrary value is a node, unaware of TypeScript inferral
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(TypeScript type).
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###### Parameters
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* `node` (`unknown`)
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— anything (typically a node)
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* `index` (`number`, optional)
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— the node’s position in its parent
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* `parent` ([`Node`][node], optional)
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— the node’s parent
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###### Returns
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Whether this is a node and passes a test (`boolean`).
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### `AssertPredicate`
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Check that an arbitrary value is a specific node, aware of TypeScript
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(TypeScript type).
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###### Type parameters
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* `Kind` ([`Node`][node])
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— node type
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###### Parameters
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* `node` (`unknown`)
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— anything (typically a node)
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* `index` (`number`, optional)
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— the node’s position in its parent
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* `parent` ([`Node`][node], optional)
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— the node’s parent
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###### Returns
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Whether this is a node and passes a test (`node is Kind`).
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### `Test`
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Check for an arbitrary node, unaware of TypeScript inferral (TypeScript
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type).
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###### Type
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```ts
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type Test =
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| null
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| undefined
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| string
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| Record<string, unknown>
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| TestFunctionAnything
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| Array<string | Record<string, unknown> | TestFunctionAnything>
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```
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Checks that the given thing is a node, and then:
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* when `string`, checks that the node has that tag name
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* when `function`, see [`TestFunctionAnything`][testfunctionanything]
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* when `object`, checks that all keys in test are in node, and that they have
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(strictly) equal values
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* when `Array`, checks if one of the subtests pass
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### `TestFunctionAnything`
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Check if a node passes a test, unaware of TypeScript inferral (TypeScript
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type).
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###### Parameters
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* `node` ([`Node`][node])
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— a node
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* `index` (`number`, optional)
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— the node’s position in its parent
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* `parent` ([`Node`][node], optional)
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— the node’s parent
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###### Returns
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Whether this node passes the test (`boolean`).
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### `PredicateTest`
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Check for a node that can be inferred by TypeScript (TypeScript type).
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###### Type
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```ts
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type PredicateTest<Kind extends Node> =
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| Kind['type']
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| Partial<Kind>
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| TestFunctionPredicate<Kind>
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| Array<Kind['type'] | Partial<Kind> | TestFunctionPredicate<Kind>>
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```
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See [`TestFunctionPredicate`][testfunctionpredicate].
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### `TestFunctionPredicate`
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Check if a node passes a certain node test (TypeScript type).
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###### Type parameters
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* `Kind` ([`Node`][node])
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— node type
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###### Parameters
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* `node` ([`Node`][node])
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— a node
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* `index` (`number`, optional)
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— the node’s position in its parent
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* `parent` ([`Node`][node], optional)
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— the node’s parent
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###### Returns
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Whether this node passes the test (`node is Kind`).
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## Examples
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### Example of `convert`
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```js
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import {u} from 'unist-builder'
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import {convert} from 'unist-util-is'
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const test = convert('leaf')
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const tree = u('tree', [
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u('node', [u('leaf', '1')]),
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u('leaf', '2'),
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u('node', [u('leaf', '3'), u('leaf', '4')]),
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u('leaf', '5')
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])
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const leafs = tree.children.filter((child, index) => test(child, index, tree))
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console.log(leafs)
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```
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Yields:
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```js
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[{type: 'leaf', value: '2'}, {type: 'leaf', value: '5'}]
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```
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## Types
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This package is fully typed with [TypeScript][].
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It exports the additional types [`AssertAnything`][assertanything],
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[`AssertPredicate`][assertpredicate], [`Test`][test],
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[`TestFunctionAnything`][testfunctionanything],
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[`TestFunctionPredicate`][testfunctionpredicate], and
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[`PredicateTest`][predicatetest].
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## Compatibility
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Projects maintained by the unified collective are compatible with all maintained
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versions of Node.js.
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As of now, that is Node.js 14.14+ and 16.0+.
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Our projects sometimes work with older versions, but this is not guaranteed.
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## Related
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* [`unist-util-find-after`](https://github.com/syntax-tree/unist-util-find-after)
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— find a node after another node
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* [`unist-util-find-before`](https://github.com/syntax-tree/unist-util-find-before)
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— find a node before another node
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* [`unist-util-find-all-after`](https://github.com/syntax-tree/unist-util-find-all-after)
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— find all nodes after another node
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* [`unist-util-find-all-before`](https://github.com/syntax-tree/unist-util-find-all-before)
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— find all nodes before another node
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* [`unist-util-find-all-between`](https://github.com/mrzmmr/unist-util-find-all-between)
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— find all nodes between two nodes
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* [`unist-util-filter`](https://github.com/syntax-tree/unist-util-filter)
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— create a new tree with nodes that pass a check
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* [`unist-util-remove`](https://github.com/syntax-tree/unist-util-remove)
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— remove nodes from tree
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## Contribute
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See [`contributing.md`][contributing] in [`syntax-tree/.github`][health] for
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ways to get started.
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See [`support.md`][support] for ways to get help.
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This project has a [code of conduct][coc].
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By interacting with this repository, organization, or community you agree to
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abide by its terms.
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## License
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[MIT][license] © [Titus Wormer][author]
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<!-- Definitions -->
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[build-badge]: https://github.com/syntax-tree/unist-util-is/workflows/main/badge.svg
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[build]: https://github.com/syntax-tree/unist-util-is/actions
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[coverage-badge]: https://img.shields.io/codecov/c/github/syntax-tree/unist-util-is.svg
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[coverage]: https://codecov.io/github/syntax-tree/unist-util-is
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[downloads-badge]: https://img.shields.io/npm/dm/unist-util-is.svg
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[downloads]: https://www.npmjs.com/package/unist-util-is
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[size-badge]: https://img.shields.io/bundlephobia/minzip/unist-util-is.svg
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[size]: https://bundlephobia.com/result?p=unist-util-is
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[sponsors-badge]: https://opencollective.com/unified/sponsors/badge.svg
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[backers-badge]: https://opencollective.com/unified/backers/badge.svg
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[collective]: https://opencollective.com/unified
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[chat-badge]: https://img.shields.io/badge/chat-discussions-success.svg
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[chat]: https://github.com/syntax-tree/unist/discussions
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[npm]: https://docs.npmjs.com/cli/install
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[esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c
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[esmsh]: https://esm.sh
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[typescript]: https://www.typescriptlang.org
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[license]: license
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[author]: https://wooorm.com
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[health]: https://github.com/syntax-tree/.github
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[contributing]: https://github.com/syntax-tree/.github/blob/main/contributing.md
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[support]: https://github.com/syntax-tree/.github/blob/main/support.md
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[coc]: https://github.com/syntax-tree/.github/blob/main/code-of-conduct.md
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[unist]: https://github.com/syntax-tree/unist
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[node]: https://github.com/syntax-tree/unist#node
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[hast-util-is-element]: https://github.com/syntax-tree/hast-util-is-element
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[unist-util-select]: https://github.com/syntax-tree/unist-util-select
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[is]: #isnode-test-index-parent-context
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[convert]: #converttest
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[assertanything]: #assertanything
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[assertpredicate]: #assertpredicate
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[test]: #test
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[testfunctionanything]: #testfunctionanything
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[testfunctionpredicate]: #testfunctionpredicate
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[predicatetest]: #predicatetest
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