gem-hunter

Constate

Basic example

import constate from "constate";
import { useState } from "react";

// 1️⃣ Create a custom hook as usual
function useCounter() {
  const [count, setCount] = useState(0);
  const increment = () => setCount((prevCount) => prevCount + 1);
  return { count, increment };
}

// 2️⃣ Wrap your hook with the constate factory
const [CounterProvider, useCounterContext] = constate(useCounter);

function Button() {
  // 3️⃣ Use context instead of custom hook
  const { increment } = useCounterContext();
  return <button onClick={increment}>+</button>;
}

function Count() {
  // 4️⃣ Use context in other components
  const { count } = useCounterContext();
  return <span>{count}</span>;
}

function App() {
  // 5️⃣ Wrap your components with Provider
  return (
    <CounterProvider>
      <Count />
      <Button />
    </CounterProvider>
  );
}

Advanced example

import constate from "constate";
import { useCallback, useState } from "react";

// 1️⃣ Create a custom hook that receives props
function useCounter({ initialCount = 0 }) {
  const [count, setCount] = useState(initialCount);
  // 2️⃣ Wrap your updaters with useCallback or use dispatch from useReducer
  const increment = useCallback(() => setCount((prev) => prev + 1), []);
  return { count, increment };
}

// 3️⃣ Wrap your hook with the constate factory splitting the values
const [CounterProvider, useCount, useIncrement] = constate(
  useCounter,
  (value) => value.count, // becomes useCount
  (value) => value.increment, // becomes useIncrement
);

function Button() {
  // 4️⃣ Use the updater context that will never trigger a re-render
  const increment = useIncrement();
  return <button onClick={increment}>+</button>;
}

function Count() {
  // 5️⃣ Use the state context in other components
  const count = useCount();
  return <span>{count}</span>;
}

function App() {
  // 6️⃣ Wrap your components with Provider passing props to your hook
  return (
    <CounterProvider initialCount={10}>
      <Count />
      <Button />
    </CounterProvider>
  );
}

Installation

npm i constate

yarn add constate

pnpm add constate

API

constate(useValue[, ...selectors])

useValue

import constate from "constate";
import { useState } from "react";

const [CountProvider, useCountContext] = constate(() => {
  const [count] = useState(0);
  return count;
});

const [CountProvider, useCountContext] = constate(({ initialCount = 0 }) => {
  const [count] = useState(initialCount);
  return count;
});

function App() {
  return <CountProvider initialCount={10}>...</CountProvider>;
}

function Count() {
  const count = useCountContext();
  console.log(count); // 10
}

selectors

import constate from "constate";
import { useCallback, useState } from "react";

function useCounter() {
  const [count, setCount] = useState(0);
  // increment's reference identity will never change
  const increment = useCallback(() => setCount((prev) => prev + 1), []);
  return { count, increment };
}

const [Provider, useCount, useIncrement] = constate(
  useCounter,
  (value) => value.count, // becomes useCount
  (value) => value.increment, // becomes useIncrement
);

function Button() {
  // since increment never changes, this will never trigger a re-render
  const increment = useIncrement();
  return <button onClick={increment}>+</button>;
}

function Count() {
  const count = useCount();
  return <span>{count}</span>;
}

Contributing

License