unified

Project: syntax-tree/unist-util-visit-parents

Package: unist-util-visit-parents@5.1.1

  1. Dependents: 0
  2. unist utility to recursively walk over nodes, with ancestral information
  1. util 147
  2. utility 143
  3. unist 133
  4. tree 44
  5. ast 37
  6. unist-util 25
  7. check 11
  8. walk 8
  9. visit 6
  10. parent 2
  11. parents 2

unist-util-visit-parents

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unist utility to walk the tree with a stack of parents.

Contents

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 and want to know about every parent of each node. You can use unist-util-visit if you don’t care about the entire stack of parents.

Install

This package is ESM only. In Node.js (version 12.20+, 14.14+, 16.0+, 18.0+), install with npm:

npm install unist-util-visit-parents

In Deno with esm.sh:

import {visitParents} from "https://esm.sh/unist-util-visit-parents@5"

In browsers with esm.sh:

<script type="module">
  import {visitParents} from "https://esm.sh/unist-util-visit-parents@5?bundle"
</script>

Use

import {visitParents} from 'unist-util-visit-parents'
import {fromMarkdown} from 'mdast-util-from-markdown'

const tree = fromMarkdown('Some *emphasis*, **strong**, and `code`.')

visitParents(tree, 'strong', (node, ancestors) => {
  console.log(node.type, ancestors.map(ancestor => ancestor.type))
})

Yields:

strong ['root', 'paragraph']

API

This package exports the identifiers visitParents, SKIP, CONTINUE, and EXIT. There is no default export.

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

Walk the tree (Node) and visit inclusive descendants with ancestral information.

This algorithm performs depth-first tree traversal in preorder (NLR), or if reverse is given, in reverse preorder (NRL).

You can choose for which nodes visitor is called by passing a test.

Walking the tree is an intensive task. Make use of the return values of the visitor when possible. Instead of walking a tree multiple times with different tests, walk it once without a test, and use unist-util-is to check if a node matches a test, and then perform different operations.

You can change the tree. See visitor below for more info.

Parameters

next? = visitor(node, ancestors)

Called when a node (matching test, if given) is entered.

Visitors are free to change node. They can also transform the parent of node (the last of ancestors). Replacing node itself is okay if SKIP is returned. When adding or removing previous siblings (or next siblings, in case of reverse) of node, visitor must return a new index (number) to specify the sibling to move to after node is traversed. Adding or removing next siblings of node (or previous siblings, in case of reverse) is fine without needing to return a new index. Replacing the children of a node is fine, but replacing them on an ancestor is not okay and still causes them to be visited.

Parameters
Returns

The return value can have the following forms:

👉 Note: yielding a tuple only makes sense if the action is SKIP. Otherwise, if the action is EXIT, that action can be returned. Or if the action is CONTINUE, index can be returned.

action

An action can have the following values:

index

Next index (number). Defines that the sibling at index should be moved to (after node itself is completely traversed). Useful if mutating the tree, such as removing the node the visitor is currently on, or any of its previous siblings (or next siblings, in case of reverse). Results less than 0 or greater than or equal to children.length stop traversing the parent

Types

This package is fully typed with TypeScript. It exports the additional types Test, Action, Index, ActionTuple, VisitorResult, and Visitor.

It also exports the types BuildVisitor<Tree extends Node = Node, Check extends Test = string> to properly type visitors from a tree and a test, and Visitor<Visited extends Node = Node, Ancestor extends Parent = Parent> to build an arbitrary visitor, from unist-util-visit-parents/complex-types.d.ts.

Compatibility

Projects maintained by the unified collective are compatible with all maintained versions of Node.js. As of now, that is Node.js 12.20+, 14.14+, 16.0+, and 18.0+. Our projects sometimes work with older versions, but this is not guaranteed.

Contribute

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

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

License

MIT © Titus Wormer