204 lines
5.6 KiB
Markdown
204 lines
5.6 KiB
Markdown
# 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**][unist] utility to check if a node passes a test.
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## Install
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[npm][]:
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```sh
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npm install unist-util-is
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```
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## Use
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```js
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var is = require('unist-util-is')
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var node = {type: 'strong'}
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var parent = {type: 'paragraph', children: [node]}
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function test(node, n) {
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return n === 5
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}
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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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```
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## API
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### `is(node[, test[, index, parent[, context]]])`
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###### Parameters
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* `node` ([`Node`][node]) — Node to check.
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* `test` ([`Function`][test], `string`, `Object`, or `Array.<Test>`, optional)
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— When nullish, checks if `node` is a [`Node`][node].
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When `string`, works like passing `node => node.type === test`.
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When `array`, checks if any one of the subtests pass.
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When `object`, checks that all keys in `test` are in `node`,
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and that they have strictly equal values
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* `index` (`number`, optional) — [Index][] of `node` in `parent`
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* `parent` ([`Node`][node], optional) — [Parent][] of `node`
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* `context` (`*`, optional) — Context object to invoke `test` with
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###### Returns
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`boolean` — Whether `test` passed *and* `node` is a [`Node`][node] (object with
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`type` set to a non-empty `string`).
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#### `function test(node[, index, parent])`
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###### Parameters
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* `node` ([`Node`][node]) — Node to check
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* `index` (`number?`) — [Index][] of `node` in `parent`
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* `parent` ([`Node?`][node]) — [Parent][] of `node`
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###### Context
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`*` — The to `is` given `context`.
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###### Returns
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`boolean?` — Whether `node` matches.
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### `is.convert(test)`
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Create a test function from `test`, that can later be called with a `node`,
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`index`, and `parent`.
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Useful if you’re going to test many nodes, for example when creating a utility
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where something else passes an is-compatible test.
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The created function is slightly faster because it expects valid input only.
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Therefore, passing invalid input, yields unexpected results.
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Can also be accessed with `require('unist-util-is/convert')`.
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For example:
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```js
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var u = require('unist-builder')
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var convert = require('unist-util-is/convert')
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var test = convert('leaf')
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var 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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var 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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## 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` in `syntax-tree/.github`][contributing] for ways to get
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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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[license]: license
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[author]: https://wooorm.com
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[contributing]: https://github.com/syntax-tree/.github/blob/HEAD/contributing.md
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[support]: https://github.com/syntax-tree/.github/blob/HEAD/support.md
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[coc]: https://github.com/syntax-tree/.github/blob/HEAD/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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[parent]: https://github.com/syntax-tree/unist#parent-1
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[index]: https://github.com/syntax-tree/unist#index
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[test]: #function-testnode-index-parent
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