hast-util-to-estree

hast utility to transform to estree (JSX).

What is this?
When should I use this?
Install
Use
API
- toEstree(tree, options?)
Types
Compatibility
Security
Related
Contribute
License

What is this?

This package is a utility that takes a hast (HTML) syntax tree as input and turns it into an estree (JavaScript) syntax tree JSX extension. This package also supports embedded MDX nodes.

When should I use this?

This project is useful when you want to embed HTML as JSX inside JS while working with syntax trees. This us used in MDX.

Install

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

npm install hast-util-to-estree

In Deno with esm.sh:

import {toEstree} from 'https://esm.sh/hast-util-to-estree@2'

In browsers with esm.sh:

<script type="module">
  import {toEstree} from 'https://esm.sh/hast-util-to-estree@2?bundle'
</script>

Use

Say our module example.html contains:

<!doctype html>
<html lang=en>
<title>Hi!</title>
<link rel=stylesheet href=index.css>
<h1>Hello, world!</h1>
<a download style="width:1;height:10px"></a>
<!--commentz-->
<svg xmlns="http://www.w3.org/2000/svg">
  <title>SVG `&lt;ellipse&gt;` element</title>
  <ellipse
    cx="120"
    cy="70"
    rx="100"
    ry="50"
  />
</svg>
<script src="index.js"></script>

…and our module example.js looks as follows:

import fs from 'node:fs/promises'
import {fromHtml} from 'hast-util-from-html'
import {toEstree} from 'hast-util-to-estree'
import {toJs, jsx} from 'estree-util-to-js'

const hast = fromHtml(await fs.readFile('example.html'))

const estree = toEstree(hast)

console.log(toJs(estree, {handlers: jsx}).value)

…now running node example.js (and prettier) yields:

/* Commentz */
;<>
  <html lang="en">
    <head>
      <title>{'Hi!'}</title>
      {'\n'}
      <link rel="stylesheet" href="index.css" />
      {'\n'}
    </head>
    <body>
      <h1>{'Hello, world!'}</h1>
      {'\n'}
      <a
        download
        style={{
          width: '1',
          height: '10px'
        }}
      />
      {'\n'}
      {}
      {'\n'}
      <svg xmlns="http://www.w3.org/2000/svg">
        {'\n  '}
        <title>{'SVG `<ellipse>` element'}</title>
        {'\n  '}
        <ellipse cx="120" cy="70" rx="100" ry="50" />
        {'\n'}
      </svg>
      {'\n'}
      <script src="index.js" />
      {'\n'}
    </body>
  </html>
</>

API

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

`toEstree(tree, options?)`

Transform to estree (JSX).

`options`

Configuration (optional).

`options.space`

Whether tree is in the HTML or SVG space (enum, 'svg' or 'html', default: 'html'). If an svg element is found when inside the HTML space, toEstree automatically switches to the SVG space when entering the element, and switches back when exiting

`options.handlers`

Object mapping node types to functions handling the corresponding nodes. See the code for examples.

Returns

Node (Program) whose last child in body is most likely an ExpressionStatement, whose expression is a JSXFragment or a JSXElement.

Typically, there is only one node in body, however, this utility also supports embedded MDX nodes in the HTML (when mdast-util-mdx is used with mdast to parse markdown before passing its nodes through to hast). When MDX ESM import/exports are used, those nodes are added before the fragment or element in body.

Note

Comments are both attached to the tree in their neighbouring nodes (recast and babel style), and added as a comments array on the program node (espree style). You may have to do program.comments = null for certain compilers.

There aren’t many great estree serializers out there that support JSX. To do that, you can use estree-util-to-js. Or, use estree-util-build-jsx to turn JSX into function calls, and then serialize with whatever (astring, escodegen).

Types

This package is fully typed with TypeScript. It exports the additional types Options, Space, and Handle.

Compatibility

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.

Security

You’re working with JavaScript. It’s not safe.

hastscript — hyperscript compatible interface for creating nodes
hast-util-from-dom — transform a DOM tree to hast
estree-util-build-jsx — transform JSX to function calls

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

Current Tags

2.3.2 ... latest (3 years ago)

5 Versions

2.3.2 ... 3 years ago
2.1.0 ... 3 years ago
2.0.2 ... 4 years ago
2.0.0 ... 4 years ago
1.4.0 ... 4 years ago