unist-util-visit

What is unist-util-visit?

The unist-util-visit package is a utility for visiting nodes in a unist syntax tree. It allows for traversal of the tree and application of functions to nodes that match specified conditions. This can be useful for manipulating or inspecting the tree in various ways, such as filtering nodes, applying transformations, or extracting information.

What are unist-util-visit's main functionalities?

Visiting nodes

This feature allows you to visit all nodes in a unist syntax tree that match a specified type. The provided function is called for each matching node. This can be useful for performing operations on specific types of nodes.

visit(tree, 'type', node => { console.log(node) })

Visiting nodes with a test function

This feature allows you to visit all nodes that pass a test implemented by a function. The test function is called with each node, and if it returns true, the node is considered a match. This allows for more complex matching conditions beyond just type.

visit(tree, node => node.value === 'specific value', node => { console.log(node) })

Exiting early

This feature allows you to exit the traversal early by returning `visit.EXIT` from the visitor function. This can be useful for optimizing performance by avoiding unnecessary traversal once a certain condition is met.

visit(tree, 'type', (node, index, parent) => { if (node.value === 'stop') return visit.EXIT })

Other packages similar to unist-util-visit

unist-util-select

This package provides a way to select nodes in a unist syntax tree using CSS-like selectors. It's similar to unist-util-visit in that it allows for node selection, but it uses a different approach based on selectors rather than explicit traversal and testing.

unist-util-filter

unist-util-filter offers functionality to create a new tree by filtering nodes in a unist syntax tree based on a given condition. It's similar to unist-util-visit in its ability to apply conditions to nodes, but instead of visiting nodes, it filters them to produce a new tree.

unist-util-map

This package allows for the creation of a new unist syntax tree by applying a function to every node in an input tree. It's related to unist-util-visit in that it involves applying functions to nodes, but unist-util-map applies the function to all nodes and constructs a new tree based on the results.

README

unist-util-visit

unist utility to visit nodes.

Install

This package is ESM only: Node 12+ is needed to use it and it must be imported instead of required.

npm:

npm install unist-util-visit

Use

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

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

visit(tree, 'leaf', (node) => {
  console.log(node)
})

Yields:

{ type: 'leaf', value: '1' }
{ type: 'leaf', value: '2' }
{ type: 'leaf', value: '3' }

Note: this example also uses unist-builder, to run the example ensure both unist-builder and unist-util-visit are installed:

npm install unist-builder unist-util-visit

API

This package exports the following identifiers: visit, CONTINUE, SKIP, and EXIT. There is no default export.

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

This function works exactly the same as unist-util-visit-parents, but visitor has a different signature.

next? = visitor(node, index, parent)

Instead of being passed an array of ancestors, visitor is called with the node’s index and its parent. The optional return value next is documented in unist-util-visit-parents’s readme.

Otherwise the same as unist-util-visit-parents.

Related

• unist-util-visit-parents — Like visit, but with a stack of parents
• unist-util-filter — Create a new tree with all nodes that pass a test
• unist-util-map — Create a new tree with all nodes mapped by a given function
• unist-util-flatmap — Create a new tree by mapping (to an array) with the given function
• unist-util-remove — Remove nodes from a tree that pass a test
• unist-util-select — Select nodes with CSS-like selectors

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