unist utility to walk the tree with a stack of parents.
- What is this?
- When should I use this?
- Install
- Use
- API
- Types
- Compatibility
- Related
- Contribute
- License
This is a very important utility for working with unist as it lets you walk the tree.
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.
This package is ESM only. In Node.js (version 16+), install with npm:
npm install unist-util-visit-parents
In Deno with esm.sh
:
import {visitParents} from 'https://esm.sh/unist-util-visit-parents@6'
In browsers with esm.sh
:
<script type="module">
import {visitParents} from 'https://esm.sh/unist-util-visit-parents@6?bundle'
</script>
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', function (node, ancestors) {
console.log(node.type, ancestors.map(ancestor => ancestor.type))
})
Yields:
strong ['root', 'paragraph']
This package exports the identifiers CONTINUE
,
EXIT
, SKIP
, and visitParents
.
There is no default export.
Visit nodes, 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
.
For complex tests, you should test yourself in visitor
, as it will be
faster and will have improved type information.
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, walk it once, use
unist-util-is
to check if a node matches, and then perform
different operations.
You can change the tree.
See Visitor
for more info.
tree
(Node
) — tree to traversetest
(Test
, optional) —unist-util-is
-compatible testvisitor
(Visitor
) — handle each nodereverse
(boolean
, default:false
) — traverse in reverse preorder (NRL) instead of the default preorder (NLR)
Nothing (undefined
).
Continue traversing as normal (true
).
Stop traversing immediately (false
).
Do not traverse this node’s children ('skip'
).
Union of the action types (TypeScript type).
type Action = typeof CONTINUE | typeof EXIT | typeof SKIP
List with one or two values, the first an action, the second an index (TypeScript type).
type ActionTuple = [
(Action | null | undefined | void)?,
(Index | null | undefined)?
]
Build a typed Visitor
function from a tree and a test (TypeScript type).
It will infer which values are passed as node
and which as parents
.
Move to the sibling at index
next (after node itself is completely
traversed) (TypeScript type).
Useful if mutating the tree, such as removing the node the visitor is currently
on, or any of its previous siblings.
Results less than 0
or greater than or equal to children.length
stop
traversing the parent.
type Index = number
unist-util-is
compatible test (TypeScript type).
Handle a node (matching test
, if given) (TypeScript type).
Visitors are free to transform node
.
They can also transform the parent of node (the last of ancestors
).
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 an ancestor still results in them being traversed.
node
(Node
) — found nodeparents
(Array<Node>
) — ancestors ofnode
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.
Any value that can be returned from a visitor (TypeScript type).
type VisitorResult =
| Action
| ActionTuple
| Index
| null
| undefined
| void
This package is fully typed with TypeScript.
It exports the additional types Action
,
ActionTuple
, BuildVisitor
,
Index
, Test
, Visitor
, and
VisitorResult
.
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-parents@^6
, compatible with Node.js 16.
unist-util-visit
— walk the tree with one parentunist-util-filter
— create a new tree with all nodes that pass a testunist-util-map
— create a new tree with all nodes mapped by a given functionunist-util-flatmap
— create a new tree by mapping (to an array) with the given functionunist-util-remove
— remove nodes from a tree that pass a testunist-util-select
— select nodes with CSS-like selectors
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.