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react-to-webcomponent

react-to-webcomponent converts React components to custom elements! It lets you share react components as native elements that don't require mounted being through React. The custom element acts as a wrapper for the underlying react component. Use these custom elements in any framework (vue, svelte, angular, ember, canjs) the same way you would use standard HTML elements.

react-to-webcomponent:

• Works in all modern browsers. (Edge needs a customElements polyfill).
• Is 1.11KB minified and gzipped.

Basic Use

Given a react component like:

const Greeting = ({name}) => {
  return (
    <h1>Hello, {name}</h1>
  );
}

Call reactToWebComponent and customElements.define as follows:

import reactToWebComponent from "react-to-webcomponent";

const WebGreeting = reactToWebComponent(Greeting, React, ReactDOM);

customElements.define("web-greeting", WebGreeting);

Now you can use <web-greeting> like any other HTML element!

You can create it programatically:

const webGreeting = document.createElement("web-greeting");
webGreeting.name = "StandardsFan";

document.body.append(webGreeting);

webGreeting.innerHTML //-> "<h1>Hello, StandardsFan</h1>"

Or you can use it declaratively:

document.body.innerHTML = "<web-greeting></web-greeting>";

document.body.firstChild.name = "CoolBeans";

document.body.firstChild.innerHTML //-> "<h1>Hello, CoolBeans</h1>"

Working with Attributes

By default, custom elements created by reactToWebComponent only pass properties to the underlying React component. To make attributes work, you must specify your component's properties with PropTypes as follows:

const Greeting = ({ name }) => {
  return (
    <h1>Hello, {name}</h1>
  );
}

Greeting.propTypes = {
  name: PropTypes.string.isRequired
};

Now reactToWebComponent will know to look for name attributes as follows:

document.body.innerHTML = "<web-greeting name='Amazed'></web-greeting>";

document.body.firstChild.innerHTML //-> "<h1>Hello, Amazed</h1>"

Working with External Libraries

reactToWebComponent also works with react components that utilize external libraries! For instance with Material-Ui:

import { Button } from "@mui/material";
import { ThemeProvider, createTheme } from '@mui/material/styles';

interface GreetingProps {
    name: string;
    description: string;
    colorMode: "light" | "dark" | undefined;
    buttonVariant: "contained" | "text" | "outlined" | undefined;
}

export const Greeting = ({ name, description, colorMode = "light", buttonVariant = "text" }: GreetingProps) => {
    const themeMode = createTheme({
        palette: {
            mode: colorMode,
        },
    })

    return (
        <ThemeProvider theme={themeMode}>
            <main>
                <h1>Hello, {name}</h1>
                <p>{description}</p>
                <Button variant={buttonVariant}>This is the button</Button>
            </main>
        </ThemeProvider>
    );
}

document.body.innerHTML = "<web-greeting name='Sven' description='How do you do?'></web-greeting>";

Using reactToWebComponent with a few provided attributes, while also not filling out the colorMode or buttonVariant. This will cause the component to render with Theme Provider's Light Theme, and with the text variant for Material UI's Button Component

If we access those attributes (colorMode and buttonVariant):

document.body.innerHTML = "<web-greeting name='Sven' description='How do you do?' colorMode='dark' buttonVariant='contained'></web-greeting>";

The Theme Provider will use the Dark Theme instead, and the Button Component wiill use the contained variant.

Thus, using reactToWebComponent you can interat with React Components using Third Party Libraries with ease.

React 18

reactToWebComponent now supports React 18! To use the new render API, the only change needed is how ReactDOM is imported, the rest remains the same.

import React from 'react';
import * as ReactDOM from 'react-dom/client';

const Greeting = ({ name }) => {
  return (
    <h1>Hello, {name}</h1>
  );
}

const WebGreeting = reactToWebComponent(Greeting, React, ReactDOM);

customElements.define("web-greeting", WebGreeting);

Please note that by using React 18, reactToWebComponent will use the new root API. If your application needs the legacy API, please use React 17.

Setup

From NPM

To install from npm:

npm i react-to-webcomponent

CodePen

Greeting example in a CodePen

Bundled JS file available

https://unpkg.com/react-to-webcomponent/dist/react-to-webcomponent.js

API

reactToWebComponent(ReactComponent, React, ReactDOM, options) takes the following:

• ReactComponent - A react component that you want to convert to a Web Component.
• React - A version of React (or preact-compat) the component works with.
• ReactDOM - A version of ReactDOM (or preact-compat) that the component works with.
• options - An optional set of parameters.
• options.shadow - Use shadow DOM rather than light DOM.
• options.dashStyleAttributes - convert dashed-attirbutes on the web component into camelCase props for the react component

A new class inheriting from HTMLElement is returned. This class can be directly passed to customElements.define as follows:

customElements.define("web-greeting",
    reactToWebComponent(Greeting, React, ReactDOM) );

Or the class can be defined and used later:

const WebGreeting = reactToWebComponent(Greeting, React, ReactDOM);

customElements.define("web-greeting", WebGreeting);

var myGreeting = new WebGreeting();
document.body.appendChild(myGreeting);

Or the class can be extended:

class WebGreeting extends reactToWebComponent(Greeting, React, ReactDOM)
{
    disconnectedCallback(){
        super.disconnectedCallback();
        // special stuff
    }
}
customElements.define("web-greeting", WebGreeting);

Components can also be implemented using shadow DOM.

const WebGreeting = reactToWebComponent(Greeting, React, ReactDOM, { shadow: true });

customElements.define("web-greeting", WebGreeting);

var myGreeting = new WebGreeting();
document.body.appendChild(myGreeting);

var shadowContent = myGreeting.shadowRoot.children[0];

Using dashStyleAttributes to convert dashed-attributes into camelCase react props

class Greeting extends React.Component {
  render () { return <h1>Hello, { this.props.camelCaseName }</h1>; }
}
Greeting.propTypes = {
  camelCaseName: PropTypes.string.isRequired
};

customElements.define(
  "my-dashed-style-greeting",
  reactToWebComponent(Greeting, React, ReactDOM, { dashStyleAttributes: true })
);

document.body.innerHTML = "<my-dashed-style-greeting camel-case-name='Christopher'></my-dashed-style-greetingg>";

console.log(document.body.firstElementChild.innerHTML) // "<h1>Hello, Christopher</h1>"

How it works

reactToWebComponent creates a constructor function whose prototype is a Proxy. This acts as a trap for any property set on instances of the custom element. When a property is set, the proxy:

• re-renders the React component inside the custom element.
• creates an enumerable getter / setter on the instance to save the set value and avoid hitting the proxy in the future.

Also:

• Enumerable properties and values on the custom element are used as the props passed to the React component.
• The React component is not rendered until the custom element is inserted into the page.

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