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. Useful when working with mdast or retext.

Installation

npm:

npm install unist-util-is

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

Usage

var is = require('.');
var node = {
    'type': 'strong'
};
var parent = {
    'type': 'paragraph',
    'children': [node]
};

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

is(null, node); // true
is('strong', node); // true
is('emphasis', node); // false

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

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

API

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

Utility to check if a node passes a test.

Parameters:

• test (Function, string, or Node, optional) — When not given, return is return true.

  Passing a string is equal to passing function (node) {return node.type === test}.

  Passing a node is equal to passing function (node) {return node === test}.

• node (Node) — Node to test;

• index (number, optional) — Position of node in parent;

• parent (Node, optional) — Parent of node;

• context (*, optional) — Parent of node.

Returns: boolean, whether test passed.

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 this iteration passes.

License

MIT © Titus Wormer