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unist-util-visit-parentsTypeScript icon, indicating that this package has built-in type declarations

3.1.1 • Public • Published


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unist utility to visit nodes, with ancestral information.



npm install unist-util-visit-parents


var remark = require('remark')
var visit = require('unist-util-visit-parents')
var tree = remark.parse('Some _emphasis_, **importance**, and `code`.')
visit(tree, 'strong', visitor)
function visitor(node, ancestors) {


[ { type: 'root', children: [ [Object] ] },
  { type: 'paragraph',
     [ [Object],
       [Object] ] } ]


visit(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 tests, 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 traverse
  • test (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 visit.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.

  • node (Node) — Found node
  • ancestors (Array.<Node>) — Ancestors of node

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.

An action can have the following values:

  • visit.EXIT (false) — Stop traversing immediately
  • visit.CONTINUE (true) — Continue traversing as normal (same behaviour as not returning anything)
  • visit.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



See in syntax-tree/.github for ways to get started. See 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.


MIT © Titus Wormer


npm i unist-util-visit-parents

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