React Pause Champ

Isomorphic React hook providing async-aware stateful variables to components, with Suspense and Server-Side-Rendering support.

Features

• React useState-like API

  Pass an identifier and an initial value to the useChamp hook and you get the current value and a setter, almost exactly like React's useState!

• Asynchronous initializers and updates

  Any function passed as either the initial value or an update of a stateful variable can be asynchronous, either through using the async-keyword or by returning a Promise.

• Suspense

  Asynchronous state initializers and updates will trigger fallback components if wrapped in <Suspense/>-boundaries. For updates this can be managed using React's startTransition.

• Server-Side-Rendering

  The whole application can render on the server, await asynchronous data, and then hydrate on client. Transparently. With the same application code.

• Server Streaming

  Server-rendering will wait for all asynchronous initializers/updates outside of any <Suspense/>-boundaries to finish before sending the initial HTML-shell to the client. Any asynchronous initializers wrapped in a <Suspense/>-boundary will send the fallback components to the client as a part of the HTML-shell, and once they have completed they will be streamed to the client, including the stateful data, allowing for a seamless experience.

• Error Boundary compatibility

  Errors thrown in initializers and updates propagate to the closest Error Boundary, allowing for unified error-handling.

• Small size

  Around 1kB gzipped without development helpers and server components. Has zero dependencies besides React, and can be treeshaked.

Installation

npm install @m4rw3r/react-pause-champ

Dependencies

• React 18

Recommended to use createRoot/hydrateRoot on the client to use batching. On the server renderToPipeableStream/renderToReadableStream is required for asynchronous initializations and Suspense support.

Examples

import { useChamp } from "@m4rw3r/react-pause-champ";

/**
 * Plain useState replacement with SSR-support.
 */
function Counter(): JSX.Element {
  const [data, update] = useChamp("my-counter", 0);

  return (
    <div>
      <p>{counter}</p>
      <button onClick={() => update((i) => i + 1)}>Increment</button>
    </div>
  );
}

/**
 * Isomorphic asynchronous fetch with SSR- and Suspense-support.
 */
function Page({ pageId }: { pageId: string }): JSX.Element {
  const [{ title, data }] = useChamp(`page.${pageId}`, async () => {
    const { title, data } = await fetchPageData();

    return { title: title.toUpperCase(), data };
  });

  return (
    <div>
      <h2>{title}</h2>
      <p>{data}</p>
    </div>
  );
}

/**
 * Asynchronous updates.
 */
function ServerCounter(): JSX.Element {
  const [value, update] = useChamp(
    "my-async-counter",
    async () => (await fetchCounter()).value
  );

  return (
    <div>
      <p>{value}</p>
      <button
        onClick={() =>
          update(
            async (old) =>
              (await fetchCounterUpdate({ newValue: old + 1 })).value
          )
        }
      >
        Increment
      </button>
    </div>
  );
}

Frequently Asked Questions

• Uncaught Error: State '*' is already mounted in another component. when using Hot-Module-Reloading.

  This is caused by reordering components in JSX without using key. When key is skipped components will use the hooks from the previous component mounted in that "slot" instead, which will cause issues with use of useState/useRef/useEffect and so on. Pause Champ uses useRef to track component instances which can and will trigger exceptions if those values are not what it expects.