This helper function creates a custom element from a React class.

To install:

yarn add react-custom-element-builder

Here is the simplest possible use:

import createCustomElement from 'react-custom-element-builder';

window.customElements.define('my-element', createCustomElement(MyReactComponent));

You have to specify all the attributes you want to watch. Attributes are automatically coerced to props for the React component.

window.customElements.define('my-element', createCustomElement(MyReactComponent, {
  attributes: {
    name: 'Megan',
    value: undefined,
  },
}));

If the browser doesn't specify an attribute for name then the value will be megan.

You can map properties to the React component using the properties option:

window.customElements.define('my-element', createCustomElement(MyReactComponent, {
  properties: {
    images: {
      default: [],
    },
    href: {},
  },
}));

This would put images and href properties on the custom element that is then accessible via JS in the client.

Assuming that you have HTML like this:

<my-element id="foo">
</my-element>

You could have Javascript in the client like so:

document.getElementById('foo').images = [...];

And the React component would be re-rendered with the new property value.

Shocker, some HTML elements have methods on them, like play on a video element. It's not really the React way, but, if you want to do something like that, you can use the methods option.

window.customElements.define('my-video', createCustomElement(MyVideoComponent, {
  methods: {
    play() {
      this.setAttribute('playing', true);
    },
  },
}));

The point of making custom elements is for these elements to behave as you would think a native HTML element would behave. So if a native HTML element would have some methods you should add them.

For stateful components a reference to the react component is available on the _reference property. You can access that externally or within a method like so:

window.customElements.define('my-video', createCustomElement(MyVideoComponent, {
  methods: {
    play() {
      this._reference.play();
    },
  },
}));

Events will not pass from your React component up to the host page without adding the composed flag. Here is an example:

this.myRef.dispatchEvent(new CustomEvent('my-click', {
  composed: true,
}));