web-component-to-react

create universal and hydratable react wrapper for custom-elements/web-components

install

npm install web-component-to-react

Example

import React from 'react';
import toReact from 'web-component-to-react';

const MyWebComponent = toReact('my-web-component');

export default function SomeComp({ children, eventHandler }) {
  return (
    <MyWebComponent onCustom={eventHandler}>
      <span className="custom">{children}</span>
    </MyWebComponent>
  );
}

Motivation

Custom elements are coming, and even though the standard does not support server side rendering yet, approaches like stencil support ssr and pre-rendering of web-components.

So there will be a future where we implement a custom element once and then use it in all our apps, no matter if the frontend is written in jQuery, Angular or React.

But as of now there are still some bumps in the road.

As a developer, you are free to use React in your Web Components, or to use Web Components in React, or both. [...] the best solution is to write a React component that behaves as a wrapper for your Web Component.

react docs on web-components

Given we have a web-component my-web-component
Then the following code will cause multiple problems

function Cmp({ children, eventHandler }) {
  return (
    <my-web-component onBaz={eventHandler}>
      <span className="custom">{children}</span>
    </my-web-component>
  );
}

Problems

1. React does not pass custom event handlers to non-react elements
2. React also doesn't pass prop updates via setAttribute but web components rely on that in order to react to changes.
3. If the my-web-component component creates additional markup that is pre-rendered by the server, react complains about a mismatch in hydration and throws away the server markup of my-web-component
4. We can not just simply leave my-web-component alone with it's server markup since children is still a part or our react app that needs to be re-rendered on changes.
5. Solving 1. - 4. requires a lot of custom code

Api

entries

This packages exposes a main and a browser field in it's package.json. webpack and other modern bundlers will use them automatically.

If you use custom tooling, be sure to use web-component-to-react/server and web-component-to-react/browser in the respective environments.

toReact(WebComponent, options)

import toReact from 'web-component-to-react';

WebComponent: string
options: {
  Portal: string?
  toEventHandlerName: func?
  toAttributeName: func?
}

This is a convenience wrapper that combines asCustomElement and withPortal. See example for usage or read on for api.

asCustomElement(WebComponent, options)

import { asCustomElement } from 'web-component-to-react';

WebComponent: string
options: {
  toEventHandlerName: func?
  toAttributeName: func?
}

Solving Problem 1 + 2 by passing props and event handlers directly to the DOM element of the wrapped component instead of using react props.

options

toEventHandlerName: func

A function receiving propName and propValue. Must return name of the event handler or falsy for non-event-handler props.

The default implementation converts onCustom to custom for all props that start with on and have a value of type function

example

import React from 'react';
import { asCustomElement } from 'web-component-to-react';

const MyWebComponent = asCustomElement('my-web-component', {
  toEventHandlerName(key, value) {
    if (key === 'foo') {
      return 'bar';
    }

    return null;
  },
});

export default function SomeComp({ eventHandler, other }) {
  return (
    <MyWebComponent foo={eventHandler} onClick={other}>
      Test
    </MyWebComponent>
  );
}

In the background this will set myWebComponentRef.addEventListener('bar', eventHandler) while onClick will be passed as a react prop.

toAttributeName: func

A function receiving propName and propValue. Must return name of the attribute or falsy for non-attribute props.

The default implementation converts customValue to custom-value for all props that aren't an event handler according to toEventHandlerName expect for children.

example

import React from 'react';
import { asCustomElement } from 'web-component-to-react';

const MyWebComponent = asCustomElement('my-web-component', {
  toAttributeName(key, value) {
    if (key === 'foo') {
      return 'super-foo';
    }

    return null;
  },
});

export default function SomeComp({ eventHandler }) {
  return <MyWebComponent foo="bar" baz="biz" />;
}

In the background this will set myWebComponentRef.setAttribute('super-foo', 'bar') while baz will be passed as a react prop.

withPortal(WebComponent, options)

import { withPortal } from 'web-component-to-react';

WebComponent: string
options: {
  Portal: string?
}

Solving Problem 3 + 4 by moving react children of the wrapped component into a hydratable portal. The portal is then rendered into the slot of the web-component.

options

Portal: string

default: 'wcr-portal'

Name of the portal element. The same element should be used across the whole app.

License

The MIT License

Copyright (C) 2018 Hannes Diercks

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.