unist-util-visit

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[unist][github-unist] utility to walk the tree.

Contents

* What is this? * When should I use this? * Install * Use * API * visit(tree[, test], visitor[, reverse]) * CONTINUE * EXIT * SKIP * Action * ActionTuple * BuildVisitor * Index * Test * Visitor * VisitorResult * Compatibility * Related * Contribute * License

What is this?

This is a very important utility for working with unist as it lets you walk the tree.

When should I use this?

You can use this utility when you want to walk the tree. You can use [unist-util-visit-parents][github-vp] if you care about the entire stack of parents.

Install

This package is [ESM only][github-gist-esm]. In Node.js (version 16+), install with [npm][npmjs-install]:

npm install unist-util-visit

In Deno with [esm.sh][esmsh]:

import {CONTINUE, EXIT, SKIP, visit} from 'https://esm.sh/unist-util-visit@5'

In browsers with [esm.sh][esmsh]:

Use

import {fromMarkdown} from 'mdast-util-from-markdown'
import {visit} from 'unist-util-visit'
const tree = fromMarkdown('Some emphasis, strong, and code.')
visit(tree, 'text', function (node, index, parent) {
  console.log([node.value, parent ? parent.type : index])
})

Yields:

[ 'Some ', 'paragraph' ]
[ 'emphasis', 'emphasis' ]
[ ', ', 'paragraph' ]
[ 'strong', 'strong' ]
[ ', and ', 'paragraph' ]
[ '.', 'paragraph' ]

API

This package exports the identifiers [CONTINUE][api-continue], [EXIT][api-exit], [SKIP][api-skip], and [visit][api-visit]. It exports the [TypeScript][] types [ActionTuple][api-action-tuple], [Action][api-action], [BuildVisitor][api-build-visitor], [Index][api-index], [Test][api-test], [VisitorResult][api-visitor-result], and [Visitor][api-visitor]. There is no default export.

visit(tree[, test], visitor[, reverse])

This function works exactly the same as [unist-util-visit-parents][github-vp], but [Visitor][api-visitor] has a different signature.

CONTINUE

Continue traversing as normal (true).

EXIT

Stop traversing immediately (false).

SKIP

Do not traverse this node’s children ('skip').

Action

Union of the action types (TypeScript type). See [Action in unist-util-visit-parents][github-vp-action].

ActionTuple

List with an action and an index (TypeScript type). See [ActionTuple in unist-util-visit-parents][github-vp-action-tuple].

BuildVisitor

Build a typed Visitor function from a tree and a test (TypeScript type). See [BuildVisitor in unist-util-visit-parents][github-vp-build-visitor].

Index

Move to the sibling at index next (TypeScript type). See [Index in unist-util-visit-parents][github-vp-index].

Test

[unist-util-is][github-unist-util-is] compatible test (TypeScript type).

Visitor

Handle a node (matching test, if given) (TypeScript type).

Visitors are free to transform node. They can also transform parent.

Replacing node itself, if SKIP is not returned, still causes its descendants to be walked (which is a bug).

When adding or removing previous siblings of node (or next siblings, in case of reverse), the Visitor should return a new Index to specify the sibling to traverse after node is traversed. Adding or removing next siblings of node (or previous siblings, in case of reverse) is handled as expected without needing to return a new Index.

Removing the children property of parent still results in them being traversed.

###### Parameters

* node ([Node][github-unist-node]) — found node * index (number or undefined) — index of node in parent * parent ([Node][github-unist-node] or undefined) — parent of node

###### Returns

What to do next.

An Index is treated as a tuple of [CONTINUE, Index]. An Action is treated as a tuple of [Action].

Passing a tuple back only makes sense if the Action is SKIP. When the Action is EXIT, that action can be returned. When the Action is CONTINUE, Index can be returned.

VisitorResult

Any value that can be returned from a visitor (TypeScript type). See [VisitorResult in unist-util-visit-parents][github-vp-visitor-result].

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, unist-util-visit@^5, compatible with Node.js 16.

Related

* [unist-util-visit-parents][github-vp] — walk the tree with a stack of parents * unist-util-filter — create a new tree with all nodes that pass a test * unist-util-map — create a new tree with all nodes mapped by a given function * unist-util-flatmap — create a new tree by mapping (to an array) with the given function * unist-util-remove — remove nodes from a tree that pass a test * unist-util-select — select nodes with CSS-like selectors

Contribute

See [contributing.md][health-contributing] in [syntax-tree/.github][health] for ways to get started. See [support.md][health-support] for ways to get help.

This project has a [code of conduct][health-coc]. By interacting with this repository, organization, or community you agree to abide by its terms.

License

[MIT][file-license] © [Titus Wormer][wooorm]

[api-action]: #action

[api-action-tuple]: #actiontuple

[api-build-visitor]: #buildvisitor

[api-continue]: #continue

[api-exit]: #exit

[api-index]: #index

[api-skip]: #skip

[api-test]: #test

[api-visit]: #visittree-test-visitor-reverse

[api-visitor]: #visitor

[api-visitor-result]: #visitorresult

[badge-build-image]: https://github.com/syntax-tree/unist-util-visit/workflows/main/badge.svg

[badge-build-url]: https://github.com/syntax-tree/unist-util-visit/actions

[badge-coverage-image]: https://img.shields.io/codecov/c/github/syntax-tree/unist-util-visit.svg

[badge-coverage-url]: https://codecov.io/github/syntax-tree/unist-util-visit

[badge-downloads-image]: https://img.shields.io/npm/dm/unist-util-visit.svg

[badge-downloads-url]: https://www.npmjs.com/package/unist-util-visit

[badge-size-image]: https://img.shields.io/bundlejs/size/unist-util-visit

[badge-size-url]: https://bundlejs.com/?q=unist-util-visit

[esmsh]: https://esm.sh

[file-license]: license

[github-gist-esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c

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

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

[github-unist-util-is]: https://github.com/syntax-tree/unist-util-is

[github-vp]: https://github.com/syntax-tree/unist-util-visit-parents

[github-vp-action]: https://github.com/syntax-tree/unist-util-visit-parents#action

[github-vp-action-tuple]: https://github.com/syntax-tree/unist-util-visit-parents#actiontuple

[github-vp-build-visitor]: https://github.com/syntax-tree/unist-util-visit-parents#buildvisitor

[github-vp-index]: https://github.com/syntax-tree/unist-util-visit-parents#index

[github-vp-visitor-result]: https://github.com/syntax-tree/unist-util-visit-parents#visitorresult

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

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

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

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

[npmjs-install]: https://docs.npmjs.com/cli/install

[typescript]: https://www.typescriptlang.org

[wooorm]: https://wooorm.com