# hast-util-is-element

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[**hast**][hast] utility to check if a [*node*][node] is a (certain)
[*element*][element].

## Install

This package is [ESM only](https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c):
Node 12+ is needed to use it and it must be `import`ed instead of `require`d.

[npm][]:

```sh
npm install hast-util-is-element
```

## Use

```js
import {isElement} from 'hast-util-is-element'

isElement({type: 'text', value: 'foo'}) // => false

isElement({type: 'element', tagName: 'a'}, 'a') // => true

isElement({type: 'element', tagName: 'a'}, ['a', 'area']) // => true
```

## API

This package exports the following identifiers: `isElement`, `convertElement`.
There is no default export.

### `isElement(node[, test[, index, parent[, context]]])`

Check if the given value is a (certain) [*element*][element].

*   `node` ([`Node`][node]) — Node to check.
*   `test` ([`Function`][test], `string`, or `Array.<Test>`, optional)
    — When `array`, checks if any one of the subtests pass.
    When `string`, checks that the element has that tag name.
    When `function`, see [`test`][test]
*   `index` (`number`, optional) — [Index][] of `node` in `parent`
*   `parent` ([`Node`][node], optional) — [Parent][] of `node`
*   `context` (`*`, optional) — Context object to invoke `test` with

###### Returns

`boolean` — Whether `test` passed *and* `node` is an [`Element`][element].

###### Throws

`Error` — When an incorrect `test`, `index`, or `parent` is given.
A `node` that is not a node, or not an element, does not throw.

#### `function test(element[, index, parent])`

###### Parameters

*   `element` ([`Element`][element]) — Element to check
*   `index` (`number?`) — [Index][] of `node` in `parent`
*   `parent` ([`Node?`][node]) — [Parent][] of `node`

###### Context

`*` — The to `is` given `context`.

###### Returns

`boolean?` — Whether `element` matches.

### `convertElement(test)`

Create a test function from `test`, that can later be called with a `node`,
`index`, and `parent`.
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 slightly faster because it expects valid input only.
Therefore, passing invalid input, yields unexpected results.

## Security

`hast-util-is-element` does not change the syntax tree so there are no openings
for [cross-site scripting (XSS)][xss] attacks.

## Related

*   [`hast-util-has-property`](https://github.com/syntax-tree/hast-util-has-property)
    — check if a node has a property
*   [`hast-util-is-body-ok-link`](https://github.com/rehypejs/rehype-minify/tree/HEAD/packages/hast-util-is-body-ok-link)
    — check if a node is “Body OK” link element
*   [`hast-util-is-conditional-comment`](https://github.com/rehypejs/rehype-minify/tree/HEAD/packages/hast-util-is-conditional-comment)
    — check if a node is a conditional comment
*   [`hast-util-is-css-link`](https://github.com/rehypejs/rehype-minify/tree/HEAD/packages/hast-util-is-css-link)
    — check if a node is a CSS link element
*   [`hast-util-is-css-style`](https://github.com/rehypejs/rehype-minify/tree/HEAD/packages/hast-util-is-css-style)
    — check if a node is a CSS style element
*   [`hast-util-embedded`](https://github.com/syntax-tree/hast-util-embedded)
    — check if a node is an embedded element
*   [`hast-util-heading`](https://github.com/syntax-tree/hast-util-heading)
    — check if a node is a heading element
*   [`hast-util-interactive`](https://github.com/syntax-tree/hast-util-interactive)
    — check if a node is interactive
*   [`hast-util-is-javascript`](https://github.com/rehypejs/rehype-minify/tree/HEAD/packages/hast-util-is-javascript)
    — check if a node is a JavaScript script element
*   [`hast-util-labelable`](https://github.com/syntax-tree/hast-util-labelable)
    — check whether a node is labelable
*   [`hast-util-phrasing`](https://github.com/syntax-tree/hast-util-phrasing)
    — check if a node is phrasing content
*   [`hast-util-script-supporting`](https://github.com/syntax-tree/hast-util-script-supporting)
    — check if a node is a script-supporting element
*   [`hast-util-sectioning`](https://github.com/syntax-tree/hast-util-sectioning)
    — check if a node is a sectioning element
*   [`hast-util-transparent`](https://github.com/syntax-tree/hast-util-transparent)
    — check if a node is a transparent element
*   [`hast-util-whitespace`](https://github.com/syntax-tree/hast-util-whitespace)
    — check if a node is inter-element whitespace

## Contribute

See [`contributing.md` in `syntax-tree/.github`][contributing] 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]

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[license]: license

[author]: https://wooorm.com

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

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

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

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

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

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

[parent]: https://github.com/syntax-tree/unist#parent-1

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

[test]: #function-testelement-index-parent

[xss]: https://en.wikipedia.org/wiki/Cross-site_scripting