hastscript

What is hastscript?

The hastscript npm package, often abbreviated as 'h', is a utility that allows for the easy creation of HAST (Hypertext Abstract Syntax Tree) nodes. HAST is a virtual DOM representation used for parsing, manipulating, and serializing HTML and XML documents. This package is particularly useful for developers working with virtual DOMs or those who need to manipulate HTML/XML documents programmatically.

What are hastscript's main functionalities?

Creating elements

This feature allows for the creation of HAST elements. The example demonstrates creating a 'div' element with a class of 'container' and the text 'Hello, world!' as its child.

const h = require('hastscript');
const element = h('div', {className: 'container'}, 'Hello, world!');

Creating elements with children

This feature enables the creation of HAST elements that contain other elements as children. The code sample shows how to create an unordered list ('ul') with two list items ('li') as its children.

const h = require('hastscript');
const list = h('ul', [
  h('li', 'Item 1'),
  h('li', 'Item 2')
]);

Creating elements with properties

This feature allows for the creation of HAST elements with specific properties. In the example, an anchor ('a') element is created with an 'href' attribute pointing to 'https://example.com' and containing the text 'Visit Example'.

const h = require('hastscript');
const link = h('a', {href: 'https://example.com'}, 'Visit Example');

Other packages similar to hastscript

react-hyperscript

Similar to hastscript, react-hyperscript provides a way to create React elements using a hyperscript-like syntax. While hastscript is focused on creating HAST nodes for HTML/XML documents, react-hyperscript is tailored for React's virtual DOM.

virtual-dom

The virtual-dom package offers a virtual DOM implementation for efficient re-rendering of web interfaces. Unlike hastscript, which is specifically designed for creating HAST nodes, virtual-dom focuses on general virtual DOM functionality, including diffing and patching algorithms.

snabbdom

Snabbdom is a virtual DOM library that is lightweight and extensible. It shares similarities with hastscript in terms of manipulating virtual DOM trees but is more focused on being a core part of user interface rendering and updates, rather than specifically dealing with HAST nodes.

README

hastscript

hast utility to create trees with ease.

Contents

• What is this?
• When should I use this?
• Install
• Use
• API
  • h(selector?[, properties][, …children])
  • s(selector?[, properties][, …children])
  • Child
  • Properties
  • Result
• Syntax tree
• JSX
• Compatibility
• Security
• Related
• Contribute
• License

What is this?

This package is a hyperscript interface (like createElement from React and h from Vue and such) to help with creating hast trees.

When should I use this?

You can use this utility in your project when you generate hast syntax trees with code. It helps because it replaces most of the repetition otherwise needed in a syntax tree with function calls. It also helps as it improves the attributes you pass by turning them into the form that is required by hast.

You can instead use unist-builder when creating any unist nodes and xastscript when creating xast (XML) nodes.

Install

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

npm install hastscript

In Deno with esm.sh:

import {h} from 'https://esm.sh/hastscript@9'

In browsers with esm.sh:

<script type="module">
  import {h} from 'https://esm.sh/hastscript@9?bundle'
</script>

Use

import {h, s} from 'hastscript'

console.log(
  h('.foo#some-id', [
    h('span', 'some text'),
    h('input', {type: 'text', value: 'foo'}),
    h('a.alpha', {class: 'bravo charlie', download: 'download'}, [
      'delta',
      'echo'
    ])
  ])
)

console.log(
  s('svg', {viewbox: '0 0 500 500', xmlns: 'http://www.w3.org/2000/svg'}, [
    s('title', 'SVG `<circle>` element'),
    s('circle', {cx: 120, cy: 120, r: 100})
  ])
)

Yields:

{
  type: 'element',
  tagName: 'div',
  properties: {className: ['foo'], id: 'some-id'},
  children: [
    {
      type: 'element',
      tagName: 'span',
      properties: {},
      children: [{type: 'text', value: 'some text'}]
    },
    {
      type: 'element',
      tagName: 'input',
      properties: {type: 'text', value: 'foo'},
      children: []
    },
    {
      type: 'element',
      tagName: 'a',
      properties: {className: ['alpha', 'bravo', 'charlie'], download: true},
      children: [{type: 'text', value: 'delta'}, {type: 'text', value: 'echo'}]
    }
  ]
}
{
  type: 'element',
  tagName: 'svg',
  properties: {viewBox: '0 0 500 500', xmlns: 'http://www.w3.org/2000/svg'},
  children: [
    {
      type: 'element',
      tagName: 'title',
      properties: {},
      children: [{type: 'text', value: 'SVG `<circle>` element'}]
    },
    {
      type: 'element',
      tagName: 'circle',
      properties: {cx: 120, cy: 120, r: 100},
      children: []
    }
  ]
}

API

This package exports the identifiers h and s. There is no default export. It exports the additional TypeScript types Child, Properties, and Result.

The export map supports the automatic JSX runtime. You can pass hastscript or hastscript/svg to your build tool (TypeScript, Babel, SWC) with an importSource option or similar.

h(selector?[, properties][, …children])

Create virtual hast trees for HTML.

Signatures

• h(): root
• h(null[, …children]): root
• h(selector[, properties][, …children]): element

Parameters

selector

Simple CSS selector (string, optional). When string, builds an Element. When nullish, builds a Root instead. The selector can contain a tag name (foo), IDs (#bar), and classes (.baz). If the selector is a string but there is no tag name in it then h defaults to build a div element and s to a g element. selector is parsed by hast-util-parse-selector.

properties

Properties of the element (Properties, optional).

children

Children of the node (Child or Array<Child>, optional).

Returns

Created tree (Result).

Element when a selector is passed, otherwise Root.

s(selector?[, properties][, …children])

Create virtual hast trees for SVG.

Signatures, parameters, and return value are the same as h above. Importantly, the selector and properties parameters are interpreted as SVG.

Child

(Lists of) children (TypeScript type).

When strings or numbers are encountered, they are turned into Text nodes. Root nodes are treated as “fragments”, meaning that their children are used instead.

Type

type Child =
  | Array<Node | number | string | null | undefined>
  | Node
  | number
  | string
  | null
  | undefined

Properties

Map of properties (TypeScript type). Keys should match either the HTML attribute name or the DOM property name, but are case-insensitive.

Type

type Properties = Record<
  string,
  | boolean
  | number
  | string
  | null
  | undefined
  // For comma- and space-separated values such as `className`:
  | Array<number | string>
  // Accepts value for `style` prop as object.
  | Record<string, number | string>
>

Result

Result from a h (or s) call (TypeScript type).

Type

type Result = Element | Root

Syntax tree

The syntax tree is hast.

JSX

This package can be used with JSX. You should use the automatic JSX runtime set to hastscript or hastscript/svg.

👉 Note while h supports dots (.) for classes or number signs (#) for IDs in selector, those are not supported in JSX.

🪦 Legacy: you can also use the classic JSX runtime, but this is not recommended. To do so, import h (or s) yourself and define it as the pragma (plus set the fragment to null).

The Use example above can then be written like so, using inline pragmas, so that SVG can be used too:

example-html.jsx:

/** @jsxImportSource hastscript */
console.log(
  <div class="foo" id="some-id">
    <span>some text</span>
    <input type="text" value="foo" />
    <a class="alpha bravo charlie" download>
      deltaecho
    </a>
  </div>
)

example-svg.jsx:

/** @jsxImportSource hastscript/svg */
console.log(
  <svg xmlns="http://www.w3.org/2000/svg" viewbox="0 0 500 500">
    <title>SVG `&lt;circle&gt;` element</title>
    <circle cx={120} cy={120} r={100} />
  </svg>
)

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, hastscript@9, compatible with Node.js 16.

Security

Use of hastscript can open you up to a cross-site scripting (XSS) when you pass user-provided input to it because values are injected into the syntax tree.

The following example shows how an image is injected that fails loading and therefore runs code in a browser.

const tree = h()

// Somehow someone injected these properties instead of an expected `src` and
// `alt`:
const otherProps = {onError: 'alert(1)', src: 'x'}

tree.children.push(h('img', {src: 'default.png', ...otherProps}))

Yields:

<img onerror="alert(1)" src="x">

The following example shows how code can run in a browser because someone stored an object in a database instead of the expected string.

const tree = h()

// Somehow this isn’t the expected `'wooorm'`.
const username = {
  type: 'element',
  tagName: 'script',
  children: [{type: 'text', value: 'alert(2)'}]
}

tree.children.push(h('span.handle', username))

Yields:

<span class="handle"><script>alert(2)</script></span>

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

Related

• unist-builder — create unist trees
• xastscript — create xast trees
• hast-to-hyperscript — turn hast into React, Preact, Vue, etc
• hast-util-to-html — turn hast into HTML
• hast-util-to-dom — turn hast into DOM trees
• estree-util-build-jsx — compile JSX away

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