unist-util-visit

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
• Types
• 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 if you care about the entire stack
of parents.

Install

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

 npm install unist-util-visit

In Deno with esm.sh:

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

In browsers with esm.sh:

 <script type="module">
  import {CONTINUE, EXIT, SKIP, visit} from 'https://esm.sh/unist-util-visit@5?bundle'
</script>

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,
EXIT, SKIP, and visit.
There is no default export.

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

This function works exactly the same as unist-util-visit-parents,
but 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.

ActionTuple

List with an action and an index (TypeScript type).
See ActionTuple in unist-util-visit-parents.

BuildVisitor

Build a typed Visitor function from a tree and a test (TypeScript type).
See BuildVisitor in unist-util-visit-parents.

Index

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

Test

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)
  — found node
• index (number or undefined)
  — index of node in parent
• parent (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.

Types

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

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
  — 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 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