hast-util-to-estree

v3.1.0

Published

8 months ago

hast utility to transform to estree (JavaScript AST) JSX

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unist hast hast-util util utility html change transform rehype estree jsx javascript ecmascript mdx

hast-util-to-estree

hast utility to transform to estree (JSX).

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 (with a 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 is used in MDX.

Install

This package is ESM only. In Node.js (version 16+), install with npm:

npm install hast-util-to-estree

In Deno with esm.sh:

import {toEstree} from 'https://esm.sh/hast-util-to-estree@3'

In browsers with esm.sh:

<script type="module">
  import {toEstree} from 'https://esm.sh/hast-util-to-estree@3?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 {jsx, toJs} from 'estree-util-to-js'
import {fromHtml} from 'hast-util-from-html'
import {toEstree} from 'hast-util-to-estree'

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 identifiers defaultHandlers and toEstree. There is no default export.

`toEstree(tree[, options])`

Transform a hast tree (with embedded MDX nodes) into an estree (with JSX nodes).

Notes

Comments

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

Frameworks

There are differences between what JSX frameworks accept, such as whether they accept class or className, or background-color or backgroundColor.

For JSX components written in MDX, the author has to be aware of this difference and write code accordingly. For hast elements transformed by this project, this will be handled through options.

| Framework | elementAttributeNameCase | stylePropertyNameCase | | --------- | -------------------------- | ----------------------- | | Preact | 'html' | 'dom' | | React | 'react' | 'dom' | | Solid | 'html' | 'css' | | Vue | 'html' | 'dom' |

Parameters

tree (HastNode) — hast tree
options (Options, optional) — configuration

Returns

estree program node (Program).

The program’s 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.

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).

`defaultHandlers`

Default handlers for elements (Record<string, Handle>).

Each key is a node type, each value is a Handle.

`ElementAttributeNameCase`

Specify casing to use for attribute names (TypeScript type).

HTML casing is for example class, stroke-linecap, xml:lang. React casing is for example className, strokeLinecap, xmlLang.

Type

type ElementAttributeNameCase = 'html' | 'react'

`Handle`

Turn a hast node into an estree node (TypeScript type).

Parameters

node (HastNode) — expected hast node
state (State) — info passed around about the current state

Returns

JSX child (JsxChild, optional).

You can also add more results to state.esm and state.comments.

`Options`

Configuration (TypeScript type).

Fields

elementAttributeNameCase (ElementAttributeNameCase, default: 'react') — specify casing to use for attribute names; this casing is used for hast elements, not for embedded MDX JSX nodes (components that someone authored manually)
handlers (Record<string, Handle>, optional) — custom handlers
space (Space, default: 'html') — which space the document is in; when an <svg> element is found in the HTML space, this package already automatically switches to and from the SVG space when entering and exiting it
stylePropertyNameCase (StylePropertyNameCase, default: 'dom') — specify casing to use for property names in style objects; this casing is used for hast elements, not for embedded MDX JSX nodes (components that someone authored manually)
tableCellAlignToStyle (boolean, default: true) — turn obsolete align props on td and th into CSS style props

`Space`

Namespace (TypeScript type).

Type

type Space = 'html' | 'svg'

`State`

Info passed around about the current state (TypeScript type).

Fields

all ((node: HastParent) => EstreeJsxChild | undefined) — transform children of a hast parent to estree
comments (Array<EstreeComment>) — list of estree comments
createJsxAttributeName ((name: string) => EstreeJsxAttributeName) — create a JSX attribute name
createJsxElementName ((name: string) => EstreeJsxElementName) — create a JSX attribute name
elementAttributeNameCase (ElementAttributeNameCase) — casing to use for attribute names
esm (Array<EstreeNode>) — list of top-level estree nodes
handle ((node: HastNode) => EstreeJsxChild | undefined) — transform a hast node to estree
inherit ((from: HastNode, to: EstreeNode) => undefined) — take positional info and data from from (use patch if you don’t want data)
patch ((from: HastNode, to: EstreeNode) => undefined) — take positional info from from (use inherit if you also want data)
schema (Schema) — current schema
stylePropertyNameCase (StylePropertyNameCase) — casing for property names in style objects
tableCellAlignToStyle (boolean) — turn obsolete align props on td and th into CSS style props

`StylePropertyNameCase`

Casing to use for property names in style objects (TypeScript type).

CSS casing is for example background-color and -webkit-line-clamp. DOM casing is for example backgroundColor and WebkitLineClamp.

Type

type StylePropertyNameCase = 'css' | 'dom'

Types

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

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, hast-util-to-estree@^3, compatible with Node.js 16.

Security

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

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

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.

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Readme

hast-util-to-estree

Contents

What is this?

When should I use this?

Install

Use

API

toEstree(tree[, options])

Notes

Comments

Frameworks

Parameters

Returns

defaultHandlers

ElementAttributeNameCase

Type

Handle

Parameters

Returns

Options

Fields

Space

Type

State

Fields

StylePropertyNameCase

Type

Types

Compatibility

Security

Related

Contribute

License

`toEstree(tree[, options])`

`defaultHandlers`

`ElementAttributeNameCase`

`Handle`

`Options`

`Space`

`State`

`StylePropertyNameCase`