unist-util-map
unist utility to create a new tree by mapping all nodes with a given function.
Contents
What is this?
This is a small utility that helps you make new trees.
When should I use this?
You can use this utility to create a new tree by mapping all nodes with a given function. Creating new trees like this can lead to performance problems, as it creates new objects for every node. When dealing with potentially large trees, and relatively few changes, use unist-util-visit
(or unist-util-visit-parents
) instead.
To remove certain nodes, you can also walk the tree with unist-util-visit
, or use unist-util-filter
(clones the tree instead of mutating) or unist-util-remove
(mutates). To create trees, use unist-builder
.
Install
This package is ESM only. In Node.js (version 16+), install with npm:
npm install unist-util-map
In Deno with esm.sh
:
import {map} from 'https://esm.sh/unist-util-map@4'
In browsers with esm.sh
:
<script type="module">
import {map} from 'https://esm.sh/unist-util-map@4?bundle'
</script>
Use
import {u} from 'unist-builder'
import {map} from 'unist-util-map'
const tree = u('tree', [
u('leaf', 'leaf 1'),
u('node', [u('leaf', 'leaf 2')]),
u('void'),
u('leaf', 'leaf 3')
])
const next = map(tree, function (node) {
return node.type === 'leaf'
? Object.assign({}, node, {value: 'CHANGED'})
: node
})
console.dir(next, {depth: undefined})
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 andtree
is not mutated.
API
This package exports the identifier map
. There is no default export.
map(tree, mapFunction)
Create a new tree by mapping all nodes with the given function.
Parameters
tree
(Node
) — tree to mapmapFunction
(MapFunction
) — function called with a node, its index, and its parent to produce a new node
Returns
New mapped tree (Node
).
MapFunction
Function called with a node, its index, and its parent to produce a new node (TypeScript type).
Parameters
node
(Node
) — node to mapindex
(number
orundefined
) — index ofnode
inparent
(if any)parent
(Node
orundefined
) — parent ofnode
Returns
New mapped node (Node
).
The children on the returned node are not used. If the original node has children, those are mapped instead.
Types
This package is fully typed with TypeScript. It exports the additional type MapFunction
.
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-map@^4
, compatible with Node.js 16.
Related
unist-util-filter
— create a new tree with all nodes that pass the given functionunist-util-flatmap
— create a new tree by expanding a node into manyunist-util-remove
— remove nodes from treesunist-util-select
— select nodes with CSS-like selectorsunist-util-visit
— walk treesunist-builder
— create trees
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.