unist-util-visit-parents
unist utility to visit nodes, with ancestral information.
Install
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
Use
import remark from 'remark'
import {visitParents} from 'unist-util-visit-parents'
var tree = remark.parse('Some _emphasis_, **importance**, and `code`.')
visitParents(tree, 'strong', visitor)
function visitor(node, ancestors) {
console.log(ancestors)
}
Yields:
[ { type: 'root', children: [ [Object] ] },
{ type: 'paragraph',
children:
[ [Object],
[Object],
[Object],
[Object],
[Object],
[Object],
[Object] ] } ]
API
This package exports the following identifiers: visitParents
, SKIP
,
CONTINUE
, and EXIT
.
There is no default export.
visitParents(tree[, test], visitor[, reverse])
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.
Parameters
tree
(Node
) — Tree to traversetest
(Test
, optional) — is
-compatible test (such as a
type)visitor
(Function) — Function invoked when a node is found
that passes test
reverse
(boolean
, default: false
) — The tree is traversed in
preorder (NLR), visiting the node itself, then its head, etc.
When reverse
is passed, the tree is traversed in reverse preorder (NRL):
the node itself is visited, then its tail, etc.
next? = visitor(node, ancestors)
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.
Parameters
node
(Node
) — Found nodeancestors
(Array.<Node>
) — Ancestors of node
Returns
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 an action
,
the second and index
.
Note that passing a tuple only makes sense if the action
is SKIP
.
If the action
is EXIT
, that action can be returned.
If the action
is CONTINUE
, index
can be returned.
action
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
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
Related
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