unist-util-map-postorder

unist utility to create a new tree by mapping all nodes in postorder traversal with a given function.

Install

This package is ESM only. In Node.js, install with npm:

npm install unist-util-map-postorder

Use

import { u } from 'unist-builder';
import { map } from 'unist-util-map-postorder';

const tree = u('tree', [
  u('leaf', 'leaf 1'),
  u('node', [u('leaf', 'leaf 2')]),
  u('void'),
  u('leaf', 'leaf 3'),
]);

const next = map(tree, (node) => {
  return node.type === 'leaf' ? Object.assign({}, node, { value: 'CHANGED' }) : node;
});

console.dir(next, { depth: null });

Yields:

{
  type: 'tree',
  children: [
    {type: 'leaf', value: 'CHANGED'},
    {type: 'node', children: [{type: 'leaf', value: 'CHANGED'}]},
    {type: 'void'},
    {type: 'leaf', value: 'CHANGED'}
  ]
}

Note: next is a changed clone and tree is not mutated.

The given function was applied in postorder traversal.

More features:

• Support replacing the original node with an array of nodes returned(E.g. replace a node by its children). Returning an empty array will delete.
  • This feature can also be archived using unist-util-flatmap or unist-util-reduce.
• Also exported a mapAsync that supports async function.

Related

• unist-util-map — create a new tree with all nodes mapped by a given function
• unist-util-reduce - recursively reduce a tree
• unist-util-flatmap — create a new tree by expanding a node into many
• unist-util-filter — create a new tree with all nodes that pass the given function
• unist-util-remove — remove nodes from trees
• unist-util-select — select nodes with CSS-like selectors
• unist-util-visit — walk trees
• unist-builder — create trees