Project: syntax-tree/unist-util-filter

Package: unist-util-filter@4.0.0

  1. Dependents: 0
  2. unist utility to create a new tree with nodes that pass a filter
  1. util 136
  2. utility 132
  3. unist 128
  4. tree 31
  5. ast 29
  6. unist-util 25
  7. node 23
  8. test 6
  9. filter 5


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


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.


This package is ESM only. In Node.js (version 12.20+, 14.14+, 16.0+, 18.0+), install with npm:

npm install unist-util-filter

In Deno with esm.sh:

import {filter} from "https://esm.sh/unist-util-filter@4"

In browsers with esm.sh:

<script type="module">
  import {filter} from "https://esm.sh/unist-util-filter@4?bundle"


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})


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


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

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

Create a new tree (Node) of copies of all nodes that pass test. (Test from unist-util-is). The tree is walked in preorder (NLR), visiting the node itself, then its head, etc.


Configuration (optional).


Whether to drop parent nodes if they had children, but all their children were filtered out (boolean, default: true).


New filtered tree (Node?). null is returned if tree itself didn’t pass the test, or is cascaded away.


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


Projects maintained by the unified collective are compatible with all maintained versions of Node.js. As of now, that is Node.js 12.20+, 14.14+, 16.0+, and 18.0+. Our projects sometimes work with older versions, but this is not guaranteed.


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.


MIT © Eugene Sharygin