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    hast-util-to-estree
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    2.2.1 • Public • Published

    hast-util-to-estree

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    hast utility to transform to estree (JSX).

    Contents

    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 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>

    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 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 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.

    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.

    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
    space

    Which space the document is in (Space, default: 'html').

    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.

    handlers

    Object mapping node types to functions handling the corresponding nodes (Record<string, Handle>, optional).

    Merged into the defaults. See Handle.

    Space

    Namespace (TypeScript type).

    Type
    type Space = 'html' | 'svg'

    State

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

    Fields
    • schema (Schema) — current schema
    • comments (Array<EstreeComment>) — list of estree comments
    • esm (Array<EstreeNode>) — list of top-level estree nodes
    • handle ((node: HastNode) => EstreeJsxChild | void) — transform a hast node to estree
    • handle ((node: HastParent) => EstreeJsxChild | void) — transform children of a hast parent to estree
    • patch ((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 name
    • createJsxElementName ((name: string) => EstreeJsxElementName) — create a JSX attribute name

    Types

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

    Compatibility

    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.

    Security

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

    Related

    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

    MIT © Titus Wormer

    Install

    npm i hast-util-to-estree

    DownloadsWeekly Downloads

    428,091

    Version

    2.2.1

    License

    MIT

    Unpacked Size

    57.3 kB

    Total Files

    25

    Last publish

    Collaborators

    • wooorm
    • kmck