hast-util-to-estree
Advanced tools
The `hast-util-to-estree` package is a utility that converts HAST (Hypertext Abstract Syntax Tree) to ESTree (ECMAScript Tree). This is particularly useful for projects that need to manipulate HTML or Markdown content and then transform it into JavaScript code structures.
Convert HAST to ESTree
This feature allows you to convert a HAST node into an ESTree node. The code sample demonstrates converting a simple HAST node representing a <div> element into its ESTree equivalent.
const toEstree = require('hast-util-to-estree');
const hast = { type: 'element', tagName: 'div', properties: {}, children: [] };
const estree = toEstree(hast);
console.log(estree);Handling different HAST node types
This feature shows how the utility handles different types of HAST nodes, including text nodes. The code sample converts a HAST node representing a <p> element with text content into its ESTree equivalent.
const toEstree = require('hast-util-to-estree');
const hast = { type: 'element', tagName: 'p', properties: {}, children: [{ type: 'text', value: 'Hello, world!' }] };
const estree = toEstree(hast);
console.log(estree);The `rehype-parse` package is used to parse HTML into HAST. While it doesn't convert HAST to ESTree, it is often used in conjunction with `hast-util-to-estree` to first parse HTML and then convert it to JavaScript structures.
The `unist-util-visit` package is a utility for traversing Unist syntax trees, which include HAST. It doesn't convert HAST to ESTree but can be used to manipulate HAST nodes before conversion.
hast utility to transform to estree (JSX).
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.
This project is useful when you want to embed HTML as JSX inside JS while working with syntax trees. This is used in MDX.
This package is ESM only. In Node.js (version 14.14+ and 16.0+), 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>
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 `<ellipse>` 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>
</>
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).
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.
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' |
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).
defaultHandlersDefault handlers for elements (Record<string, Handle>).
Each key is a node type, each value is a Handle.
ElementAttributeNameCaseSpecify 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 ElementAttributeNameCase = 'html' | 'react'
HandleTurn a hast node into an estree node (TypeScript type).
JSX child (JsxChild, optional).
You can also add more results to state.esm and state.comments.
OptionsConfiguration (TypeScript type).
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 handlersspace (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 itstylePropertyNameCase
(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)SpaceNamespace (TypeScript type).
type Space = 'html' | 'svg'
StateInfo passed around about the current state (TypeScript type).
schema (Schema)
— current schemaelementAttributeNameCase
(ElementAttributeNameCase)
— casing to use for attribute namescomments (Array<EstreeComment>)
— list of estree commentsesm (Array<EstreeNode>)
— list of top-level estree nodeshandle ((node: HastNode) => EstreeJsxChild | void)
— transform a hast node to estreehandle ((node: HastParent) => EstreeJsxChild | void)
— transform children of a hast parent to estreepatch ((from: HastNode, to: EstreeNode) => void)
— take positional info from from (use inherit if you also want data)inherit ((from: HastNode, to: EstreeNode) => void)
— take positional info and data from from (use patch if you don’t want
data)createJsxAttributeName ((name: string) => EstreeJsxAttributeName)
— create a JSX attribute namecreateJsxElementName ((name: string) => EstreeJsxElementName)
— create a JSX attribute nameStylePropertyNameCaseCasing 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 StylePropertyNameCase = 'dom' | 'css'
This package is fully typed with TypeScript.
It exports the additional types
ElementAttributeNameCase,
Handle, Options,
Space, State, and
StylePropertyNameCase.
Projects maintained by the unified collective are compatible with all maintained versions of Node.js. As of now, that is Node.js 14.14+ and 16.0+. Our projects sometimes work with older versions, but this is not guaranteed.
You’re working with JavaScript. It’s not safe.
hastscript
— hyperscript compatible interface for creating nodeshast-util-from-dom
— transform a DOM tree to hastestree-util-build-jsx
— transform JSX to function callsSee 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.
FAQs
hast utility to transform to estree (JavaScript AST) JSX
The npm package hast-util-to-estree receives a total of 655,522 weekly downloads. As such, hast-util-to-estree popularity was classified as popular.
We found that hast-util-to-estree demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 2 open source maintainers collaborating on the project.
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