README.md

valtio-signal

Another React binding for Valtio proxy state

What it is

To use Valtio proxy state, the official method is useSnapshot. There's alternative library called use-valtio.

This library provides yet another method. It follows jotai-signal, which is inspired by @preact/signals-react.

It allows to use the proxy state in React without using hooks. We don't need to follow the rules of hooks.

How to use it

/** @jsxImportSource valtio-signal */

import { proxy } from 'valtio/vanilla';
import { $ } from 'valtio-signal';

const state = proxy({ count: 0 });

setInterval(() => {
  ++state.count;
}, 100);

const Counter = () => <div>Count: {$(state).count}</div>;

How it works

The pragma at the first line does the trick. It will transform the code with signal to the code that React can handle.

Original code

/** @jsxImportSource valtio-signal */

const Counter = () => (
  <div>
    Count: {$(state).count} ({Math.random()})
  </div>
);

Pseudo transformed code

import { useEffect, useMemo, useReducer } from 'react';
import { snapshot, subscribe } from 'valtio';

const Counter = () => {
  const [, rerender] = useReducer((c) => c + 1, 0);
  useEffect(() => {
    let lastValue;
    const unsubscribe = subscribe(() => {
      const nextValue = snapshot(state).count;
      if (lastValue !== nextValue) {
        lastValue = nextValue;
        rerender();
      }
    });
    return unsubscribe;
  }, []);
  return (
    <div>
      {(useMemo(() => 'Count: '), [])}
      {snapshot(state).count}
      {useMemo(() => ` (${Math.random()})`, [])}
    </div>
  );
};