Learn about our RFC process, Open RFC meetings & more.Join in the discussion! »

constate

3.0.1 • Public • Published

constate logo

Constate

NPM version NPM downloads Size Dependencies Build Status Coverage Status

Write local state using React Hooks and lift it up to React Context only when needed with minimum effort.


🕹 CodeSandbox demos 🕹
Counter I18n Theming TypeScript Wizard Form

Basic example

import React, { useState } from "react";
import constate from "constate";
 
// 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>
  );
}

Learn more

Advanced example

import React, { useState, useCallback } from "react";
import constate from "constate";
 
// 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>
  );
}

Learn more

Installation

npm:

npm i constate

Yarn:

yarn add constate

API

constate(useValue[, ...selectors])

Constate exports a single factory method. As parameters, it receives useValue and optional selector functions. It returns a tuple of [Provider, ...hooks].

useValue

It's any custom hook:

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

You can receive props in the custom hook function. They will be populated with <Provider />:

const [CountProvider, useCountContext] = constate(({ initialCount = 0 }) => {
  const [count] = useState(initialCount);
  return count;
});
 
function App() {
  return (
    <CountProvider initialCount={10}>
      ...
    </CountProvider>
  );
}

The API of the containerized hook returns the same value(s) as the original, as long as it is a descendant of the Provider:

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

selectors

Optionally, you can pass in one or more functions to split the custom hook value into multiple React Contexts. This is useful so you can avoid unnecessary re-renders on components that only depend on a part of the state.

A selector function receives the value returned by useValue and returns the value that will be held by that particular Context.

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

If you find a bug, please create an issue providing instructions to reproduce it. It's always very appreciable if you find the time to fix it. In this case, please submit a PR.

If you're a beginner, it'll be a pleasure to help you contribute. You can start by reading the beginner's guide to contributing to a GitHub project.

When working on this codebase, please use yarn. Run yarn examples to run examples.

License

MIT © Diego Haz

Keywords

Install

npm i constate

DownloadsWeekly Downloads

36,830

Version

3.0.1

License

MIT

Unpacked Size

23.9 kB

Total Files

10

Last publish

Collaborators

  • avatar