unist-util-filter

What is unist-util-filter?

The `unist-util-filter` package is a utility for filtering nodes in a Unist syntax tree. It allows you to traverse and selectively remove nodes based on a predicate function, making it useful for tasks such as cleaning up or transforming abstract syntax trees (ASTs).

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

Filter nodes based on a predicate

This feature allows you to filter nodes in a Unist tree based on a predicate function. In this example, the tree is filtered to remove paragraphs containing the text 'World'.

const filter = require('unist-util-filter');
const tree = {
  type: 'root',
  children: [
    { type: 'paragraph', children: [{ type: 'text', value: 'Hello' }] },
    { type: 'paragraph', children: [{ type: 'text', value: 'World' }] }
  ]
};
const filteredTree = filter(tree, node => node.type !== 'paragraph' || node.children[0].value !== 'World');
console.log(filteredTree);

Filter nodes with a specific type

This feature allows you to filter out nodes of a specific type. In this example, all 'heading' nodes are removed from the tree.

const filter = require('unist-util-filter');
const tree = {
  type: 'root',
  children: [
    { type: 'paragraph', children: [{ type: 'text', value: 'Hello' }] },
    { type: 'heading', children: [{ type: 'text', value: 'Title' }] }
  ]
};
const filteredTree = filter(tree, node => node.type !== 'heading');
console.log(filteredTree);

Other packages similar to unist-util-filter

unist-util-visit

The `unist-util-visit` package is used for traversing Unist syntax trees. Unlike `unist-util-filter`, which removes nodes based on a predicate, `unist-util-visit` allows you to visit nodes and perform actions on them. It is more focused on traversal and manipulation rather than filtering.

unist-util-map

The `unist-util-map` package allows you to transform nodes in a Unist tree by applying a function to each node. While `unist-util-filter` is used for removing nodes, `unist-util-map` is used for transforming nodes, making it useful for different kinds of tree manipulations.

unist-util-remove

The `unist-util-remove` package is specifically designed for removing nodes from a Unist tree based on a predicate. It is similar to `unist-util-filter` but focuses solely on the removal aspect, without the additional filtering capabilities.

README

unist-util-filter

unist utility to create a new tree with only nodes that pass a test.

Contents

• What is this?
• When should I use this?
• Install
• Use
• API
  • filter(tree[, options][, test])
  • Options
• Types
• Compatibility
• Related
• Contribute
• License

What is this?

This is a small utility that helps you clean a tree.

When should I use this?

You can use this utility to remove things from a tree. This utility is very similar to unist-util-remove, which changes the given tree. Modifying a tree like that utility does is much faster on larger documents.

You can also walk the tree with unist-util-visit to remove nodes. To create trees, use unist-builder.

Install

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

npm install unist-util-filter

In Deno with esm.sh:

import {filter} from 'https://esm.sh/unist-util-filter@5'

In browsers with esm.sh:

<script type="module">
  import {filter} from 'https://esm.sh/unist-util-filter@5?bundle'
</script>

Use

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

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

const newTree = filter(tree, node => node.type !== 'leaf' || node.value % 2 === 0)

console.dir(newTree, {depth: null})

Yields:

{
  type: 'root',
  children: [
    {type: 'parent', children: [{type: 'leaf', value: '2'}]},
    {type: 'leaf', value: '4'}
  ]
}

API

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

filter(tree[, options][, test])

Create a new tree of copies of all nodes that pass test.

The tree is walked in preorder (NLR), visiting the node itself, then its head, etc.

Parameters

• tree (Node) — tree to filter
• options (Options, optional) — configuration
• test (Test, optional) — unist-util-is compatible test

Returns

New filtered tree (Node or undefined).

undefined is returned if tree itself didn’t pass the test, or is cascaded away.

Options

Configuration (TypeScript type).

Fields

• cascade (boolean, default: true) — whether to drop parent nodes if they had children, but all their children were filtered out

Types

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

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-filter@^5, compatible with Node.js 16.

Related

• unist-util-visit — walk the tree
• unist-util-visit-parents — walk the tree with a stack of parents
• 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) by a 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 © Eugene Sharygin