328 lines
9.9 KiB
Markdown
328 lines
9.9 KiB
Markdown
# hast-util-is-element
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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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[hast][] utility to check if a node is a (certain) element.
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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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* [`isElement(element[, test[, index, parent[, context]]])`](#iselementelement-test-index-parent-context)
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* [`convertElement(test)`](#convertelementtest)
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* [`Check`](#check)
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* [`Test`](#test)
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* [`TestFunction`](#testfunction)
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* [Types](#types)
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* [Compatibility](#compatibility)
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* [Security](#security)
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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 element.
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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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elements nodes are.
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A similar package, [`unist-util-is`][unist-util-is], works on any unist node.
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For more advanced tests, [`hast-util-select`][hast-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 16+), install with [npm][]:
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```sh
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npm install hast-util-is-element
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```
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In Deno with [`esm.sh`][esmsh]:
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```js
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import {isElement} from 'https://esm.sh/hast-util-is-element@3'
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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 {isElement} from 'https://esm.sh/hast-util-is-element@3?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 {isElement} from 'hast-util-is-element'
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isElement({type: 'text', value: 'foo'}) // => false
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isElement({type: 'element', tagName: 'a', properties: {}, children: []}) // => true
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isElement({type: 'element', tagName: 'a', properties: {}, children: []}, 'a') // => true
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isElement({type: 'element', tagName: 'a', properties: {}, children: []}, 'b') // => false
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isElement({type: 'element', tagName: 'a', properties: {}, children: []}, ['a', 'area']) // => true
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```
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## API
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This package exports the identifiers
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[`convertElement`][api-convert-element] and
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[`isElement`][api-is-element].
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There is no default export.
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### `isElement(element[, test[, index, parent[, context]]])`
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Check if `element` is an `Element` and whether it passes the given test.
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###### Parameters
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* `element` (`unknown`, optional)
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— thing to check, typically [`Node`][hast-node]
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* `test` ([`Test`][api-test], optional)
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— check for a specific element
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* `index` (`number`, optional)
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— position of `element` in its parent
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* `parent` ([`Parent`][hast-parent], optional)
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— parent of `element`
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* `context` (`unknown`, optional)
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— context object (`this`) to call `test` with
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###### Returns
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Whether `element` is an `Element` 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 `element` is not a node or not an element.
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### `convertElement(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 `element`, `index`, and `parent`.
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###### Parameters
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* `test` ([`Test`][api-test], optional)
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— a test for a specific element
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###### Returns
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A check ([`Check`][api-check]).
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### `Check`
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Check that an arbitrary value is an element (TypeScript type).
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###### Parameters
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* `this` (`unknown`, optional)
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— context object (`this`) to call `test` with
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* `element` (`unknown`)
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— anything (typically an element)
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* `index` (`number`, optional)
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— position of `element` in its parent
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* `parent` ([`Parent`][hast-parent], optional)
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— parent of `element`
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###### Returns
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Whether this is an element and passes a test (`boolean`).
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### `Test`
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Check for an arbitrary element (TypeScript type).
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* when `string`, checks that the element has that tag name
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* when `function`, see [`TestFunction`][api-test-function]
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* when `Array`, checks if one of the subtests pass
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###### Type
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```ts
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type Test =
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| Array<TestFunction | string>
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| TestFunction
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| string
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| null
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| undefined
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```
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### `TestFunction`
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Check if an element passes a test (TypeScript type).
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###### Parameters
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* `element` ([`Element`][hast-element])
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— an element
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* `index` (`number` or `undefined`)
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— position of `element` in its parent
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* `parent` ([`Parent`][hast-parent] or `undefined`)
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— parent of `element`
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###### Returns
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Whether this element passes the test (`boolean`, optional).
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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 [`Check`][api-check],
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[`Test`][api-test], and
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[`TestFunction`][api-test-function].
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## Compatibility
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Projects maintained by the unified collective are compatible with maintained
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versions of Node.js.
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When we cut a new major release, we drop support for unmaintained versions of
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Node.
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This means we try to keep the current release line, `hast-util-is-element@^3`,
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compatible with Node.js 16.
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## Security
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`hast-util-is-element` does not change the syntax tree so there are no openings
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for [cross-site scripting (XSS)][xss] attacks.
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## Related
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* [`hast-util-has-property`](https://github.com/syntax-tree/hast-util-has-property)
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— check if a node has a property
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* [`hast-util-is-body-ok-link`](https://github.com/rehypejs/rehype-minify/tree/main/packages/hast-util-is-body-ok-link)
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— check if a node is “Body OK” link element
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* [`hast-util-is-conditional-comment`](https://github.com/rehypejs/rehype-minify/tree/main/packages/hast-util-is-conditional-comment)
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— check if a node is a conditional comment
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* [`hast-util-is-css-link`](https://github.com/rehypejs/rehype-minify/tree/main/packages/hast-util-is-css-link)
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— check if a node is a CSS link element
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* [`hast-util-is-css-style`](https://github.com/rehypejs/rehype-minify/tree/main/packages/hast-util-is-css-style)
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— check if a node is a CSS style element
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* [`hast-util-embedded`](https://github.com/syntax-tree/hast-util-embedded)
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— check if a node is an embedded element
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* [`hast-util-heading`](https://github.com/syntax-tree/hast-util-heading)
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— check if a node is a heading element
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* [`hast-util-interactive`](https://github.com/syntax-tree/hast-util-interactive)
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— check if a node is interactive
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* [`hast-util-is-javascript`](https://github.com/rehypejs/rehype-minify/tree/main/packages/hast-util-is-javascript)
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— check if a node is a JavaScript script element
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* [`hast-util-labelable`](https://github.com/syntax-tree/hast-util-labelable)
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— check whether a node is labelable
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* [`hast-util-phrasing`](https://github.com/syntax-tree/hast-util-phrasing)
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— check if a node is phrasing content
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* [`hast-util-script-supporting`](https://github.com/syntax-tree/hast-util-script-supporting)
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— check if a node is a script-supporting element
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* [`hast-util-sectioning`](https://github.com/syntax-tree/hast-util-sectioning)
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— check if a node is a sectioning element
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* [`hast-util-transparent`](https://github.com/syntax-tree/hast-util-transparent)
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— check if a node is a transparent element
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* [`hast-util-whitespace`](https://github.com/syntax-tree/hast-util-whitespace)
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— check if a node is inter-element whitespace
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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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<!-- Definition -->
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[build-badge]: https://github.com/syntax-tree/hast-util-is-element/workflows/main/badge.svg
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[build]: https://github.com/syntax-tree/hast-util-is-element/actions
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[coverage-badge]: https://img.shields.io/codecov/c/github/syntax-tree/hast-util-is-element.svg
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[coverage]: https://codecov.io/github/syntax-tree/hast-util-is-element
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[downloads-badge]: https://img.shields.io/npm/dm/hast-util-is-element.svg
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[downloads]: https://www.npmjs.com/package/hast-util-is-element
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[size-badge]: https://img.shields.io/badge/dynamic/json?label=minzipped%20size&query=$.size.compressedSize&url=https://deno.bundlejs.com/?q=hast-util-is-element
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[size]: https://bundlejs.com/?q=hast-util-is-element
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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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[hast]: https://github.com/syntax-tree/hast
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[hast-node]: https://github.com/syntax-tree/hast#nodes
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[hast-parent]: https://github.com/syntax-tree/hast#parent
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[hast-element]: https://github.com/syntax-tree/hast#element
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[xss]: https://en.wikipedia.org/wiki/Cross-site_scripting
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[unist-util-is]: https://github.com/syntax-tree/unist-util-is
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[hast-util-select]: https://github.com/syntax-tree/hast-util-select
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[api-is-element]: #iselementelement-test-index-parent-context
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[api-convert-element]: #convertelementtest
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[api-check]: #check
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[api-test]: #test
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[api-test-function]: #testfunction
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