@b9g/crank

Try Crank

The fastest way to try Crank is via the online playground. In addition, many of the code examples in these guides feature live previews.

Installation

The Crank package is available on NPM through the @b9g organization (short for bikeshaving).

npm i @b9g/crank

Importing Crank with the classic JSX transform.

/** @jsx createElement */
/** @jsxFrag Fragment */
import {createElement, Fragment} from "@b9g/crank";
import {renderer} from "@b9g/crank/dom";

renderer.render(
  <p>This paragraph element is transpiled with the classic transform.</p>,
  document.body,
);

Importing Crank with the automatic JSX transform.

/** @jsxImportSource @b9g/crank */
import {renderer} from "@b9g/crank/dom";

renderer.render(
  <p>This paragraph element is transpiled with the automatic transform.</p>,
  document.body,
);

You will likely have to configure your tools to support JSX, especially if you do not want to use @jsx comment pragmas. See below for common tools and configurations.

Importing the JSX template tag.

Starting in version 0.5, the Crank package ships a tagged template function which provides similar syntax and semantics as the JSX transform. This allows you to write Crank components in vanilla JavaScript.

import {jsx} from "@b9g/crank/standalone";
import {renderer} from "@b9g/crank/dom";

renderer.render(jsx`
  <p>No transpilation is necessary with the JSX template tag.</p>
`, document.body);

ECMAScript Module CDNs

Crank is also available on CDNs like unpkg (https://unpkg.com/@b9g/crank?module) and esm.sh (https://esm.sh/@b9g/crank) for usage in ESM-ready environments.

/** @jsx createElement */

// This is an ESM-ready environment!
// If code previews work, your browser is an ESM-ready environment!

import {createElement} from "https://unpkg.com/@b9g/crank/crank?module";
import {renderer} from "https://unpkg.com/@b9g/crank/dom?module";

renderer.render(
  <div id="hello">
    Running on <a href="https://unpkg.com">unpkg.com</a>
  </div>,
  document.body,
);

Common tool configurations

The following is an incomplete list of configurations to get started with Crank.

TypeScript

TypeScript is a typed superset of JavaScript.

Here’s the configuration you will need to set up automatic JSX transpilation.

{
  "compilerOptions": {
    "jsx": "react-jsx",
    "jsxImportSource": "@b9g/crank"
  }
}

The classic transform is supported as well.

{
  "compilerOptions": {
    "jsx": "react",
    "jsxFactory": "createElement",
    "jsxFragmentFactory": "Fragment"
  }
}

Crank is written in TypeScript. Refer to the guide on TypeScript for more information about Crank types.

import type {Context} from "@b9g/crank";
function *Timer(this: Context) {
  let seconds = 0;
  const interval = setInterval(() => {
    seconds++;
    this.refresh();
  }, 1000);
  for ({} of this) {
    yield <div>Seconds: {seconds}</div>;
  }

  clearInterval(interval);
}

Babel

Babel is a popular open-source JavaScript compiler which allows you to write code with modern syntax (including JSX) and run it in environments which do not support the syntax.

Here is how to get Babel to transpile JSX for Crank.

Automatic transform:

{
  "plugins": [
    "@babel/plugin-syntax-jsx",
    [
      "@babel/plugin-transform-react-jsx",
      {
        "runtime": "automatic",
        "importSource": "@b9g/crank",

        "throwIfNamespace": false,
        "useSpread": true
      }
    ]
  ]
}

Classic transform:

{
  "plugins": [
    "@babel/plugin-syntax-jsx",
    [
      "@babel/plugin-transform-react-jsx",
      {
        "runtime": "class",
        "pragma": "createElement",
        "pragmaFrag": "''",

        "throwIfNamespace": false,
        "useSpread": true
      }
    ]
  ]
}

ESLint

ESLint is a popular open-source tool for analyzing and detecting problems in JavaScript code.

Crank provides a configuration preset for working with ESLint under the package name eslint-plugin-crank.

npm i eslint eslint-plugin-crank

In your eslint configuration:

{
  "extends": ["plugin:crank/recommended"]
}

Astro

Astro.js is a modern static site builder and framework.

Crank provides an Astro integration to enable server-side rendering and client-side hydration with Astro.

npm i astro-crank

In your astro.config.mjs.

import {defineConfig} from "astro/config";
import crank from "astro-crank";

// https://astro.build/config
export default defineConfig({
  integrations: [crank()],
});

Key Examples

A Simple Component

import {renderer} from "@b9g/crank/dom";

function Greeting({name = "World"}) {
  return (
    <div>Hello {name}</div>
  );
}

renderer.render(<Greeting />, document.body);

A Stateful Component

import {renderer} from "@b9g/crank/dom";

function *Timer() {
  let seconds = 0;
  const interval = setInterval(() => {
    seconds++;
    this.refresh();
  }, 1000);
  try {
    while (true) {
      yield <div>Seconds: {seconds}</div>;
    }
  } finally {
    clearInterval(interval);
  }
}

renderer.render(<Timer />, document.body);

An Async Component

import {renderer} from "@b9g/crank/dom";
async function Definition({word}) {
  // API courtesy https://dictionaryapi.dev
  const res = await fetch(`https://api.dictionaryapi.dev/api/v2/entries/en/${word}`);
  const data = await res.json();
  if (!Array.isArray(data)) {
    return <p>No definition found for {word}</p>;
  }

  const {phonetic, meanings} = data[0];
  const {partOfSpeech, definitions} = meanings[0];
  const {definition} = definitions[0];
  return <>
    <p>{word} <code>{phonetic}</code></p>
    <p><b>{partOfSpeech}.</b> {definition}</p>
  </>;
}

await renderer.render(<Definition word="framework" />, document.body);

A Loading Component

import {Fragment} from "@b9g/crank";
import {renderer} from "@b9g/crank/dom";

async function LoadingIndicator() {
  await new Promise(resolve => setTimeout(resolve, 1000));
  return <div>Fetching a good boy...</div>;
}

async function RandomDog({throttle = false}) {
  const res = await fetch("https://dog.ceo/api/breeds/image/random");
  const data = await res.json();
  if (throttle) {
    await new Promise(resolve => setTimeout(resolve, 2000));
  }

  return (
    <a href={data.message}>
      <img src={data.message} alt="A Random Dog" width="300" />
    </a>
  );
}

async function *RandomDogLoader({throttle}) {
  for await ({throttle} of this) {
    yield <LoadingIndicator />;
    yield <RandomDog throttle={throttle} />;
  }
}

function *RandomDogApp() {
  let throttle = false;
  this.addEventListener("click", (ev) => {
    if (ev.target.tagName === "BUTTON") {
      throttle = !throttle;
      this.refresh();
    }
  });

  for ({} of this) {
    yield (
      <Fragment>
        <RandomDogLoader throttle={throttle} />
        <p>
          <button>Show me another dog.</button>
        </p>
      </Fragment>
    );
  }
}

renderer.render(<RandomDogApp />, document.body);

Changelog

[0.6.1] - 2025-04-21

Features

• Added prop: and attr: prefixes to disambiguate props which should be treated as element properties vs attributes.
• Added html alias for the jsx template tag in JavaScript.

Bug Fixes

• Added missing copy prop to TypeScript types.
• Fix copy prop being rendered by HTML renderer.