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unist-util-visit-parents

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unist-util-visit-parents

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[unist][unist] utility to visit nodes, with ancestral information.

Install

[npm][]:

sh
npm install unist-util-visit-parents

Use

js
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) {
  console.log(ancestors)
}

Yields:

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

API

`visit(tree[, test], visitor[, reverse])`

Visit nodes ([*inclusive descendants*][descendant] of [tree][tree]), with ancestral information. Optionally filtering nodes. Optionally in reverse.

This algorithm performs [*depth-first*][depth-first] [*tree traversal*][tree-traversal] in [*preorder*][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][is] to check if a node matches a test, and then perform different operations.

Parameters

tree ([Node][node]) — [Tree][] to traverse
test ([Test][is], optional) — [is][is]-compatible test (such as a [type][])
visitor ([Function][visitor]) — 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 [descendant][]s to be visited. If adding or removing previous [sibling][]s (or next siblings, in case of reverse) of node, visitor should return a new [index][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][node]) — Found node
ancestors (Array.<Node>) — [Ancestor][]s of node

Returns

The return value can have the following forms:

[index][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:

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`

[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](https://github.com/syntax-tree/unist-util-visit) — Like visit-parents, but with one parent
[unist-util-filter](https://github.com/syntax-tree/unist-util-filter) — Create a new tree with all nodes that pass a test
[unist-util-map](https://github.com/syntax-tree/unist-util-map) — Create a new tree with all nodes mapped by a given function
[unist-util-flatmap](https://gitlab.com/staltz/unist-util-flatmap) — Create a new tree by mapping (to an array) with the given function
[unist-util-remove](https://github.com/syntax-tree/unist-util-remove) — Remove nodes from a tree that pass a test
[unist-util-select](https://github.com/syntax-tree/unist-util-select) — Select nodes with CSS-like selectors