Hast-util-is-element NPM

hast-util-is-element

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

What is this?

This package is a small utility that checks that a node is a certain element.

When should I use this?

Use this small utility if you find yourself repeating code for checking what elements nodes are.

A similar package, unist-util-is, works on any unist node.

For more advanced tests, hast-util-select can be used to match against CSS selectors.

Install

This package is ESM only. In Node.js (version 16+), install with npm:

npm install hast-util-is-element

In Deno with esm.sh:

import {isElement} from 'https://esm.sh/hast-util-is-element@3'

In browsers with esm.sh:

<script type="module">
  import {isElement} from 'https://esm.sh/hast-util-is-element@3?bundle'
</script>

Use

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

isElement({type: 'text', value: 'foo'}) // => false
isElement({type: 'element', tagName: 'a', properties: {}, children: []}) // => true
isElement({type: 'element', tagName: 'a', properties: {}, children: []}, 'a') // => true
isElement({type: 'element', tagName: 'a', properties: {}, children: []}, 'b') // => false
isElement({type: 'element', tagName: 'a', properties: {}, children: []}, ['a', 'area']) // => true

API

This package exports the identifiers convertElement and isElement. There is no default export.

`isElement(element[, test[, index, parent[, context]]])`

Check if element is an Element and whether it passes the given test.

Parameters

element (unknown, optional) — thing to check, typically Node
test (Test, optional) — check for a specific element
index (number, optional) — position of element in its parent
parent (Parent, optional) — parent of element
context (unknown, optional) — context object (this) to call test with

Returns

Whether element is an Element and passes a test (boolean).

Throws

When an incorrect test, index, or parent is given. There is no error thrown when element is not a node or not an element.

`convertElement(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 element, index, and parent.

Parameters

test (Test, optional) — a test for a specific element

Returns

A check (Check).

`Check`

Check that an arbitrary value is an element (TypeScript type).

Parameters

this (unknown, optional) — context object (this) to call test with
element (unknown) — anything (typically an element)
index (number, optional) — position of element in its parent
parent (Parent, optional) — parent of element

Returns

Whether this is an element and passes a test (boolean).

`Test`

Check for an arbitrary element (TypeScript type).

when string, checks that the element has that tag name
when function, see TestFunction
when Array, checks if one of the subtests pass

Type

type Test =
  | Array<TestFunction | string>
  | TestFunction
  | string
  | null
  | undefined

`TestFunction`

Check if an element passes a test (TypeScript type).

Parameters

element (Element) — an element
index (number or undefined) — position of element in its parent
parent (Parent or undefined) — parent of element

Returns

Whether this element passes the test (boolean, optional).

Types

This package is fully typed with TypeScript. It exports the additional types Check, Test, and TestFunction.

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, hast-util-is-element@^3, compatible with Node.js 16.