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unist-util-parents

unist utility to add references to parents on nodes in a tree.

Contents

• What is this?
• When should I use this?
• Install
• Use
• API
  • parents(tree)
  • Proxy
• Types
• Compatibility
• Related
• Contribute
• License

What is this?

This utility creates a proxy of the tree that acts like the original tree upon reading, but each proxied node has a reference to its parent node.

When should I use this?

This package can be very useful for problems where it is needed to figure out what a nodes ancestors are, because unist itself is a non-cyclical data structure, and thus does not provide that information. On the other hand, this info on ancestors can also be gathered when walking the tree with unist-util-visit-parents.

Install

This package is ESM only. In Node.js (version 16+), install with npm:

npm install unist-util-parents

In Deno with esm.sh:

import {parent} from 'https://esm.sh/unist-util-parents@3'

In browsers with esm.sh:

<script type="module">
  import {parent} from 'https://esm.sh/unist-util-parents@3?bundle'
</script>

Use

import {u} from 'unist-builder'
import {parents} from 'unist-util-parents'

const tree = u('root', [
  u('leaf', 'leaf 1'),
  u('node', [
    u('leaf', 'leaf 2'),
    u('void'),
    u('node', [
      u('leaf', 'leaf 3'),
      u('node', [u('leaf', 'leaf 4')]),
      u('void'),
      u('leaf', 'leaf 5')
    ])
  ])
])

const wrapped = parents(tree)

// Leaf 4
const node = wrapped.children[1].children[2].children[1].children[0]

const chain = []
while (node) {
  chain.push(node.type)
  node = node.parent
}

console.log(chain.reverse())

Yields:

['root', 'node', 'node', 'node', 'leaf']

API

This package exports the identifier parents. There is no default export.

parents(tree)

Create a proxy of tree that acts like the original tree upon reading, but each proxied node has a reference to its parent node.

Notes

The returned proxy imposes two additional fields on all of its nodes:

• parent — parent link (or undefined for the root)
• node — link to the original node

These new fields are not enumerable and the original tree is not changed. This means you can use JSON.stringify on the wrapped tree and it’s the same.

wrapped.children returns array of wrapped child nodes, so that any recursive algorithm will work on a wrapped tree just as well.

To write changes to the tree, use .node to access the original tree.

Parameters

• tree (Node) — tree to proxy

Returns

Proxy of tree (Proxy).

Proxy

A proxy of a Node that adds two additional fields:

• parent — parent link (or undefined for the root)
• node — link to the original node

Types

This package is fully typed with TypeScript. It exports the additional type Proxy.

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-parents@^3, compatible with Node.js 16.

Related

• unist-util-visit-parents — walk the tree with ancestral information

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, organisation, or community you agree to abide by its terms.

License

MIT © Eugene Sharygin