unist utility to visit nodes, with ancestral information.
This package is ESM only:
Node 12+ is needed to use it and it must be import
ed instead of require
d.
npm:
npm install unist-util-visit-parents
import {visitParents} from 'unist-util-visit-parents'
import {fromMarkdown} from 'mdast-util-from-markdown'
const tree = fromMarkdown('Some _emphasis_, **importance**, and `code`.')
visitParents(tree, 'strong', (node, ancestors) => {
console.log(node.type, ancestors)
})
Yields:
strong
[
{
type: 'root',
children: [[Object]],
position: {start: [Object], end: [Object]}
},
{
type: 'paragraph',
children: [
[Object],
[Object],
[Object],
[Object],
[Object],
[Object],
[Object]
],
position: {start: [Object], end: [Object]}
}
]
This package exports the following identifiers: visitParents
, SKIP
,
CONTINUE
, and EXIT
.
There is no default export.
Visit nodes (inclusive descendants of tree
), with
ancestral information.
Optionally filtering nodes.
Optionally in reverse.
This algorithm performs depth-first
tree traversal in preorder (NLR), or
if reverse
is given, in reverse preorder (NRL).
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 test
s, walk it once
without a test, and use unist-util-is
to check if a node matches a test,
and then perform different operations.
tree
(Node
) — Tree to traversetest
(Test
, optional) —is
-compatible test (such as a type)visitor
(Function) — Function invoked when a node is found that passestest
reverse
(boolean
, default:false
) — The tree is traversed in preorder (NLR), visiting the node itself, then its head, etc. Whenreverse
is passed, the tree is traversed in reverse preorder (NRL): the node itself is visited, then its tail, etc.
Invoked when a node (matching test
, if given) is found.
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 visited.
If adding or removing previous siblings (or next siblings, in case of
reverse
) of node
, visitor
should return a new index
(number
)
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.
The return value can have the following forms:
index
(number
) — Treated as a tuple of[CONTINUE, index]
action
(*
) — Treated as a tuple of[action]
tuple
(Array.<*>
) — List with one or two values, the first anaction
, the second andindex
. Note that passing a tuple only makes sense if theaction
isSKIP
. If theaction
isEXIT
, that action can be returned. If theaction
isCONTINUE
,index
can be returned.
An action can have the following values:
EXIT
(false
) — Stop traversing immediatelyCONTINUE
(true
) — Continue traversing as normal (same behaviour as not returning anything)SKIP
('skip'
) — Do not traverse this node’s children; continue with the specified index
index
(number
) — Move to the sibling at index
next (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
unist-util-visit
— Likevisit-parents
, but 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.