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Preact is an alternative to React with the same modern API.

Preact components are packaged using Webpacker and the Preact code is located in app/javascript.

Preact components get loaded via webpacker's helper function javascript_packs_with_chunks_tag.


Preact supports PropTypes. When creating Preact components, please ensure that you have defined your PropTypes.

Common PropTypes#

Using PropTypes can be repetitive. Some duplication is normal, like when a PropType is a string or a number. But for commonly-used PropTypes, like the user entity, you can use the provided common PropTypes, located in the /app/javascript/common-prop-types, as shown below.

import PropTypes from "prop-types";
export const userPropTypes = PropTypes.shape({  id: PropTypes.string.isRequired,  name: PropTypes.string.isRequired,  profile_image_url: PropTypes.string.isRequired,  summary: PropTypes.string.isRequired,});

Using Common PropTypes#

Common PropTypes are imported just like any other JavaScript Module. For example, here are two scenarios where a component needs to use the tagPropTypes.

In the example below, our component SomeComponentUsingTags has a tags prop, which is an array of the tag entity. PropTypes have a built-in method called arrayOf that allows you to define a prop as an array of something. In our case, this is the tag entity, so we can use the tagPropTypes PropType.

import { h } from "preact";import PropTypes from "prop-types";import { tagPropTypes } from "../../../components/common-prop-types";
const SomeComponentUsingTags = ({ tags = [] }) => (  <ul>    { => (      <li key={}>{}</li>    ))}  </ul>);
SomeComponentUsingTags.displayName = "SomeComponentUsingTags";SomeComponentUsingTags.propTypes = {  tags: PropTypes.arrayOf(tagPropTypes).isRequired,};

In the following example, the SomeComponentUsingOneTag component has a tag prop representing a single tag. In this case, we can just the tagPropTypes on their own to represent the shape of the tag prop.

import { h } from "preact";import { tagPropTypes } from "../../../components/common-prop-types";
const SomeComponentUsingOneTag = ({ tag }) => <li key={}>{}</li>;
SomeComponentUsingOneTag.displayName = "SomeComponentUsingTags";SomeComponentUsingOneTag.propTypes = {  tag: tagPropTypes.isRequired,};