diff --git a/src/content/reference/react-dom/components/index.md b/src/content/reference/react-dom/components/index.md index ec2e1d2eea1..586663398c6 100644 --- a/src/content/reference/react-dom/components/index.md +++ b/src/content/reference/react-dom/components/index.md @@ -162,23 +162,137 @@ Similar to the [DOM standard,](https://developer.mozilla.org/en-US/docs/Web/API/ ### Custom HTML elements {/*custom-html-elements*/} -If you render a tag with a dash, like ``, React will assume you want to render a [custom HTML element.](https://developer.mozilla.org/en-US/docs/Web/Web_Components/Using_custom_elements) In React, rendering custom elements works differently from rendering built-in browser tags: - -- All custom element props are serialized to strings and are always set using attributes. -- Custom elements accept `class` rather than `className`, and `for` rather than `htmlFor`. +If you render a tag with a dash, like ``, React will assume you want to render a [custom HTML element.](https://developer.mozilla.org/en-US/docs/Web/Web_Components/Using_custom_elements) If you render a built-in browser HTML element with an [`is`](https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/is) attribute, it will also be treated as a custom element. - +#### Setting values on custom elements {/*attributes-vs-properties*/} + +Custom elements have two methods of passing data into them: + +1) Attributes: Which are displayed in markup and can only be set to string values +2) Properties: Which are not displayed in markup and can be set to arbitrary JavaScript values + +By default, React will pass values bound in JSX as attributes: + +```jsx + +``` + +Non-string JavaScript values passed to custom elements will be serialized by default: + +```jsx +// Will be passed as `"1,2,3"` as the output of `[1,2,3].toString()` + +``` + +React will, however, recognize an custom element's property as one that it may pass arbitrary values to if the property name shows up on the class during construction: + + + +```js src/index.js hidden +import {MyElement} from './MyElement.js'; +import { createRoot } from 'react-dom/client'; +import {App} from "./App.js"; + +customElements.define('my-element', MyElement); + +const root = createRoot(document.getElementById('root')) +root.render(); +``` + +```js src/MyElement.js active +export class MyElement extends HTMLElement { + constructor() { + super(); + // The value here will be overwritten by React + // when initialized as an element + this.value = undefined; + } + + connectedCallback() { + this.innerHTML = this.value.join(", "); + } +} +``` -[A future version of React will include more comprehensive support for custom elements.](https://github.com/facebook/react/issues/11347#issuecomment-1122275286) +```js src/App.js +export function App() { + return +} +``` -You can try it by upgrading React packages to the most recent experimental version: + + +#### Listening for events on custom elements {/*custom-element-events*/} + +A common pattern when using custom elements is that they may dispatch [`CustomEvent`s](https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent) rather than accept a function to call when an event occur. You can listen for these events using an `on` prefix when binding to the event via JSX. + + + +```js src/index.js hidden +import {MyElement} from './MyElement.js'; +import { createRoot } from 'react-dom/client'; +import {App} from "./App.js"; + +customElements.define('my-element', MyElement); + +const root = createRoot(document.getElementById('root')) +root.render(); +``` + +```javascript src/MyElement.js +export class MyElement extends HTMLElement { + constructor() { + super(); + this.test = undefined; + this.emitEvent = this._emitEvent.bind(this); + } + + _emitEvent() { + const event = new CustomEvent('speak', { + detail: { + message: 'Hello, world!', + }, + }); + this.dispatchEvent(event); + } + + connectedCallback() { + this.el = document.createElement('button'); + this.el.innerText = 'Say hi'; + this.el.addEventListener('click', this.emitEvent); + this.appendChild(this.el); + } + + disconnectedCallback() { + this.el.removeEventListener('click', this.emitEvent); + } +} +``` + +```jsx src/App.js active +export function App() { + return ( + console.log(e.detail.message)} + > + ) +} +``` + + + + -- `react@experimental` -- `react-dom@experimental` +Events are case-sensitive and support dashes (`-`). Preserve the casing of the event and include all dashes when listening for custom element's events: -Experimental versions of React may contain bugs. Don't use them in production. +```jsx +// Listens for `say-hi` events + +// Listens for `sayHi` events + +``` ---