@rrjs/react-compat

React hooks implemented on top of signals. Designed so React code translates with minimal changes: state is read through a getter (count() instead of count). Inside JSX the Babel plugin handles this automatically.

Install

npm install @rrjs/react-compat @rrjs/signals @rrjs/renderer

Quick start

import { useState, useEffect, useMemo } from '@rrjs/react-compat'
import { h, mount } from '@rrjs/renderer'

function Counter() {
  const [count, setCount] = useState(0)
  const doubled = useMemo(() => count() * 2, [count])

  useEffect(() => {
    document.title = `Count: ${count()}`
  }, [count])

  return h('div', null,
    h('p', null, () => `${count()} → ${doubled()}`),
    h('button', { onClick: () => setCount(count() + 1) }, 'inc')
  )
}

mount(Counter, document.getElementById('app'))

Supported hooks

| Hook | Status | Notes | |---|---|---| | useState | ✓ | Returns [getter, setter]. Functional updaters supported. | | useReducer | ✓ | Returns [stateGetter, dispatch]. Lazy init supported. | | useMemo | ✓ | Returns a getter. Wrapped in computed — auto-tracks signals read inside. | | useCallback | ✓ | Standard React behavior with dep array. | | useEffect | ✓ | Fires post-paint via MessageChannel. Cleanup runs before next effect. | | useLayoutEffect | ✓ | Fires synchronously before paint. | | useRef | ✓ | Plain mutable box. | | useContext | ✓ | Stack-based propagation. createContext + Provider. | | useId | ✓ | Generates :rN:-style ids. Client-only. | | useImperativeHandle | ✓ | Pairs with forwardRef. | | useSyncExternalStore | ✓ | Subscribes to external stores (Redux, Zustand, etc.). | | useDeferredValue | — | No-op; returns input as-is. | | useTransition | — | No-op; runs synchronously. |

Forwarding refs

import { forwardRef, useRef } from '@rrjs/react-compat'

const FancyInput = forwardRef((props, ref) =>
  h('input', { ref, type: 'text', ...props })
)

function Form() {
  const inputRef = useRef(null)
  return h(FancyInput, { ref: inputRef })
}

Context

import { createContext, useContext } from '@rrjs/react-compat'

const ThemeContext = createContext('light')

function App() {
  return h(ThemeContext.Provider, { value: 'dark' },
    h(ThemedButton, null)
  )
}

function ThemedButton() {
  const theme = useContext(ThemeContext)
  return h('button', { className: theme }, 'click')
}

Nested providers are supported. Each Provider push is paired with a pop after children mount.

External stores (Redux, Zustand, etc.)

import { useSyncExternalStore } from '@rrjs/react-compat'

function Counter({ store }) {
  const state = useSyncExternalStore(store.subscribe, store.getState)
  return h('div', null, () => state().count)
}

Same contract as React 18+. Any state library that ships React bindings using useSyncExternalStore should work.

Why getters instead of values

In React, const [count, setCount] = useState(0) makes count a plain number. That works because React re-runs the entire component function on every state change — the new value of count comes from the new render.

In a signal model, the component runs once. After that, count would be frozen at the initial value forever. To stay reactive without re-running the component, count must be a function that reads the live signal. So count is a getter: count().

Inside JSX, the Babel plugin wraps {count} as () => count, and the renderer auto-invokes nested getters. So in JSX you write {count} the same as in React. Outside JSX (event handlers, useMemo factories, useEffect bodies), you call the getter: count().

License

MIT License

Copyright (c) 2026 Saman Abaasi

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.