Project: syntax-tree/mdast-zone

Package: mdast-zone@5.1.0

  1. Dependents: 0
  2. mdast utility to treat HTML comments as ranges or markers
  1. util 147
  2. utility 143
  3. unist 133
  4. html 126
  5. mdast 90
  6. mdast-util 31
  7. marker 13
  8. comment 9
  9. range 2


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mdast utility to find two comments and replace the content in them.


What is this?

This package is a utility that lets you find certain comments, then takes the content between them, and calls a given handler with the result, so that you can change or replace things.

When should I use this?

This utility is typically useful when you have certain sections that can be generated. Comments are a hidden part of markdown, so they can be used as processing instructions. You can use those comments to define what content to change or replace.

A similar package, mdast-util-heading-range, does the same but uses a heading to mark the start and end of sections.


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

npm install mdast-zone

In Deno with esm.sh:

import {zone} from 'https://esm.sh/mdast-zone@5'

In browsers with esm.sh:

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


Say we have the following file, example.md:

<!--foo start-->


<!--foo end-->

…and a module example.js:

import {read} from 'to-vfile'
import {remark} from 'remark'
import {zone} from 'mdast-zone'

const file = await remark()
  .process(await read('example.md'))


/** @type {import('unified').Plugin<[], import('mdast').Root>} */
function myPluginThatReplacesFoo() {
  return (tree) => {
    zone(tree, 'foo', (start, nodes, end) => [
      {type: 'paragraph', children: [{type: 'text', value: 'Bar.'}]},

…now running node example.js yields:

<!--foo start-->


<!--foo end-->


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

zone(tree, name, handler)

Search tree (Node) for comments marked name (string) and transform a section with handler (Function).

function handler(start, nodes, end, info)

Callback called when a range is found.




Start of range (Node), an HTML (or MDX) comment node.


Nodes between start and end (Array<Node>).


End of range (Node), an HTML (or MDX) comment node.


Extra info (Object):


Optional list of nodes to replace start, nodes, and end with (Array<Node>?).


This package is fully typed with TypeScript. This package exports the types Handler and ZoneInfo.


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+, and 16.0+. Our projects sometimes work with older versions, but this is not guaranteed.


Improper use of handler can open you up to a cross-site scripting (XSS) attack as the value it returns is injected into the syntax tree. This can become a problem if the tree is later transformed to hast. The following example shows how a script is injected that could run when loaded in a browser.

function handler(start, nodes, end) {
  return [start, {type: 'html', value: '<script>alert(1)</script>'}, end]


<!--foo start-->


<!--foo end-->

Either do not use user input or use hast-util-santize.


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 © Titus Wormer