unist-util-is

What is unist-util-is?

The unist-util-is npm package is a utility library for working with Unist nodes. Unist (Universal Syntax Tree) is part of the unified ecosystem, which provides a way to work with syntax trees for content such as Markdown, HTML, or plain text. unist-util-is specifically helps in testing and filtering nodes in these trees based on certain conditions.

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

Test nodes with a condition

This feature allows you to test if a node matches a specific type or condition. In the example, `is` is used to check if the root node is a 'leaf' (which it isn't), and then if the first child of the root is a 'leaf' (which it is).

const is = require('unist-util-is');
const u = require('unist-builder');

const tree = u('root', [
  u('leaf', 'first leaf'),
  u('node', [u('leaf', 'nested leaf')])
]);

const test = is(tree, 'leaf'); // false
const testLeaf = is(tree.children[0], 'leaf'); // true

Filter nodes by type

This feature demonstrates how to filter nodes by type using `is` in combination with `unist-util-select`. It selects all 'leaf' nodes from the tree and filters them to ensure they are of type 'leaf'.

const is = require('unist-util-is');
const u = require('unist-builder');
const select = require('unist-util-select');

const tree = u('root', [
  u('leaf', 'first leaf'),
  u('node', [u('leaf', 'nested leaf')])
]);

const leaves = select.selectAll('leaf', tree).filter(node => is(node, 'leaf'));

Other packages similar to unist-util-is

unist-util-visit

This package is similar to unist-util-is in that it is used to work with Unist nodes. However, unist-util-visit focuses on visiting nodes within a tree, optionally filtering nodes, and applying a function to each node. It differs from unist-util-is by providing traversal capabilities rather than just testing or filtering.

unist-util-select

unist-util-select is used to select nodes from a Unist tree using CSS-like selectors. It complements unist-util-is by providing a way to retrieve nodes based on complex queries, whereas unist-util-is is more focused on testing nodes against specified conditions.

README

unist-util-is

Unist utility to check if a node passes a test.

Installation

npm:

npm install unist-util-is

Usage

var is = require('unist-util-is');

var node = {type: 'strong'};
var parent = {type: 'paragraph', children: [node]};

function test(node, n) { return n === 5 }

is(); // false
is(null, {children: []}); // false
is(null, node); // true
is('strong', node); // true
is('emphasis', node); // false

is(node, node) // true
is({type: 'paragraph'}, parent) // true
is({type: 'strong'}, parent) // false

is(test, node); // false
is(test, node, 4, parent); // false
is(test, node, 5, parent); // true

API

is(test, node[, index, parent[, context]])

Parameters

• test (Function, string, Object, or Array.<Test>, optional) — When not given, checks if node is a Node. When string, works like passing function (node) {return node.type === test}. When array, checks any one of the subtests pass. When object, checks that all keys in test are in node, and that they have (strictly) equal values
• node (Node) — Node to check. false is returned
• index (number, optional) — Position of node in parent
• parent (Node, optional) — Parent of node
• context (*, optional) — Context object to invoke test with

Returns

boolean — Whether test passed and node is a Node (object with type set to non-empty string).

function test(node[, index, parent])

Parameters

• node (Node) — Node to test
• index (number?) — Position of node in parent
• parent (Node?) — Parent of node

Context

* — The to is given context.

Returns

boolean? — Whether node matches.

Related

• unist-util-find-after — Find a node after another node
• unist-util-find-before — Find a node before another node
• unist-util-find-all-after — Find all nodes after another node
• unist-util-find-all-before — Find all nodes before another node
• unist-util-find-all-between — Find all nodes between two nodes
• unist-util-find — Find nodes matching a predicate
• unist-util-filter — Create a new tree with nodes that pass a check
• unist-util-remove — Remove nodes from tree

License

MIT © Titus Wormer