unist-util-visit-parents
v6.0.1
Published
unist utility to recursively walk over nodes, with ancestral information
Downloads
65,643,730
Readme
unist-util-visit-parents
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 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>
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', function (node, ancestors) {
console.log(node.type, ancestors.map(ancestor => ancestor.type))
})
Yields:
strong ['root', 'paragraph']
API
This package exports the identifiers CONTINUE
,
EXIT
, SKIP
, and visitParents
.
There is no default export.
visitParents(tree[, test], visitor[, reverse])
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.
Parameters
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)
Returns
Nothing (undefined
).
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).
Type
type Action = typeof CONTINUE | typeof EXIT | typeof SKIP
ActionTuple
List with one or two values, the first an action, the second an index (TypeScript type).
Type
type ActionTuple = [
(Action | null | undefined | void)?,
(Index | null | undefined)?
]
BuildVisitor
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
.
Type parameters
Returns
Index
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
type Index = number
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 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.
Parameters
node
(Node
) — found nodeparents
(Array<Node>
) — ancestors ofnode
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).
Type
type VisitorResult =
| Action
| ActionTuple
| Index
| null
| undefined
| void
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-parents@^6
, compatible with Node.js 16.
Related
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
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.