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 node visitor. Useful when working with mdast or retext.

Installation

npm:

npm install unist-util-visit

unist-util-visit is also available for bower, component, and duo, and as an AMD, CommonJS, and globals module, uncompressed and compressed.

Usage

var mdast = require('mdast');
var visit = require('unist-util-visit');

mdast().use(function (ast) {
    visit(ast, 'text', console.log.bind(console));
}).process('Some *emphasis*, **strongness**, and `code`.');

Yields:

{'type': 'text', 'value': 'Some '}
{'type': 'text', 'value': 'emphasis'}
{'type': 'text', 'value': ', '}
{'type': 'text', 'value': 'strongness'}
{'type': 'text', 'value': ', and '}
{'type': 'text', 'value': '.'}

API

visit(node[, type], callback[, reverse])

visit is synchronous.

Visit nodes. Optionally by node type. Optionally in reverse.

• node (Node) — Unist node;

• type (string, optional) — Optional node type to invoke callback for. By default, all nodes are visited.

• callback (function(node, index?, parent?)) — Callback invoked when a node (matching type?) is found. Invoked with the node, its index in parent (or null), and its parent (or null).

  Can return false to immediately stop checking.

• reverse (boolean, default: false, optional) — When falsey, checking starts at the first child and continues through to later children. When truthy, this is reversed.

  This does not mean checking starts at the deepest node and continues on to the highest node.

License

MIT © Titus Wormer