219 lines
6.9 KiB
Markdown
219 lines
6.9 KiB
Markdown
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# unist-util-visit-parents
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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 visit nodes, with ancestral information.
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## Install
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[npm][]:
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```sh
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npm install unist-util-visit-parents
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```
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## Usage
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```js
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var remark = require('remark')
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var visit = require('unist-util-visit-parents')
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var tree = remark.parse('Some _emphasis_, **importance**, and `code`.')
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visit(tree, 'strong', visitor)
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function visitor(node, ancestors) {
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console.log(ancestors)
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}
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```
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Yields:
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```js
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[ { type: 'root', children: [ [Object] ] },
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{ type: 'paragraph',
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children:
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[ [Object],
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[Object],
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[Object],
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[Object],
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[Object],
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[Object],
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[Object] ] } ]
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```
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## API
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### `visit(tree[, test], visitor[, reverse])`
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Visit nodes ([**inclusive descendants**][descendant] of [`tree`][tree]), with
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ancestral information. Optionally filtering nodes. Optionally in reverse.
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###### Parameters
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* `tree` ([`Node`][node]) — [Tree][] to traverse
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* `test` ([`Test`][is], optional) — [`is`][is]-compatible test (such as a
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[type][])
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* `visitor` ([Function][visitor]) — Function invoked when a node is found
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that passes `test`
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* `reverse` (`boolean`, default: `false`) — The tree is walked in [preorder][]
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(NLR), visiting the node itself, then its [head][], etc.
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When `reverse` is passed, the tree is stilled walked in preorder, but now
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in NRL (the node itself, then its [tail][], etc.)
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#### `next? = visitor(node, ancestors)`
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Invoked when a node (matching `test`, if given) is found.
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Visitors are free to transform `node`.
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They can also transform the [parent][] of node (the last of `ancestors`).
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Replacing `node` itself, if `visit.SKIP` is not returned, still causes its
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[descendant][]s to be visited.
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If adding or removing previous [sibling][]s (or next siblings, in case of
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`reverse`) of `node`, `visitor` should return a new [`index`][index] (`number`)
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to specify the sibling to traverse after `node` is traversed.
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Adding or removing next siblings of `node` (or previous siblings, in case of
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reverse) is handled as expected without needing to return a new `index`.
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Removing the `children` property of parent still results in them being
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traversed.
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###### Parameters
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* `node` ([`Node`][node]) — Found node
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* `ancestors` (`Array.<Node>`) — [Ancestor][]s of `node`
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##### Returns
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The return value can have the following forms:
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* [`index`][index] (`number`) — Treated as a tuple of `[CONTINUE, index]`
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* `action` (`*`) — Treated as a tuple of `[action]`
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* `tuple` (`Array.<*>`) — List with one or two values, the first an `action`,
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the second and `index`.
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Note that passing a tuple only makes sense if the `action` is `SKIP`.
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If the `action` is `EXIT`, that action can be returned.
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If the `action` is `CONTINUE`, `index` can be returned.
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###### `action`
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An action can have the following values:
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* `visit.EXIT` (`false`) — Stop traversing immediately
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* `visit.CONTINUE` (`true`) — Continue traversing as normal (same behaviour
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as not returning anything)
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* `visit.SKIP` (`'skip'`) — Do not traverse this node’s children; continue
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with the specified index
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###### `index`
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[`index`][index] (`number`) — Move to the sibling at `index` next (after `node`
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itself is completely traversed).
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Useful if mutating the tree, such as removing the node the visitor is currently
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on, or any of its previous siblings (or next siblings, in case of `reverse`)
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Results less than `0` or greater than or equal to `children.length` stop
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traversing the parent
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## Related
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* [`unist-util-visit`](https://github.com/syntax-tree/unist-util-visit)
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— Like `visit-parents`, but with one parent
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* [`unist-util-filter`](https://github.com/eush77/unist-util-filter)
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— Create a new tree with all nodes that pass a test
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* [`unist-util-map`](https://github.com/syntax-tree/unist-util-map)
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— Create a new tree with all nodes mapped by a given function
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* [`unist-util-flatmap`](https://gitlab.com/staltz/unist-util-flatmap)
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— Create a new tree by mapping (to an array) with the provided function and
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then flattening
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* [`unist-util-remove`](https://github.com/eush77/unist-util-remove)
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— Remove nodes from a tree that pass a test
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* [`unist-util-select`](https://github.com/eush77/unist-util-select)
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— Select nodes with CSS-like selectors
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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, organisation, 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://img.shields.io/travis/syntax-tree/unist-util-visit-parents.svg
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[build]: https://travis-ci.org/syntax-tree/unist-util-visit-parents
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[coverage-badge]: https://img.shields.io/codecov/c/github/syntax-tree/unist-util-visit-parents.svg
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[coverage]: https://codecov.io/github/syntax-tree/unist-util-visit-parents
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[downloads-badge]: https://img.shields.io/npm/dm/unist-util-visit-parents.svg
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[downloads]: https://www.npmjs.com/package/unist-util-visit-parents
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[size-badge]: https://img.shields.io/bundlephobia/minzip/unist-util-visit-parents.svg
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[size]: https://bundlephobia.com/result?p=unist-util-visit-parents
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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/join%20the%20community-on%20spectrum-7b16ff.svg
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[chat]: https://spectrum.chat/unified/syntax-tree
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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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[unist]: https://github.com/syntax-tree/unist
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[node]: https://github.com/syntax-tree/unist#node
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[visitor]: #next--visitornode-ancestors
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[contributing]: https://github.com/syntax-tree/.github/blob/master/contributing.md
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[support]: https://github.com/syntax-tree/.github/blob/master/support.md
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[coc]: https://github.com/syntax-tree/.github/blob/master/code-of-conduct.md
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[is]: https://github.com/syntax-tree/unist-util-is
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[preorder]: https://www.geeksforgeeks.org/tree-traversals-inorder-preorder-and-postorder/
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[descendant]: https://github.com/syntax-tree/unist#descendant
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[head]: https://github.com/syntax-tree/unist#head
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[tail]: https://github.com/syntax-tree/unist#tail
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[parent]: https://github.com/syntax-tree/unist#parent-1
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[sibling]: https://github.com/syntax-tree/unist#sibling
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[index]: https://github.com/syntax-tree/unist#index
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[ancestor]: https://github.com/syntax-tree/unist#ancestor
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[tree]: https://github.com/syntax-tree/unist#tree
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[type]: https://github.com/syntax-tree/unist#type
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