README.md

useStateWithCallback React Hook

Custom hook to include a callback function for useState which was previously available for setState in class components. Read more about it here.

Installation

npm install use-state-with-callback

Usage

useStateWithCallback:

import * as React from 'react';

import useStateWithCallback from 'use-state-with-callback';

// Note: cannot be used on the server-side (e.g. Next.js)
// import { useStateWithCallbackInstant } from 'use-state-with-callback';

const App = () => {
  const [count, setCount] = useStateWithCallback(0, currentCount => {
    console.log('render, then callback.');
    console.log('otherwise use useStateWithCallbackInstant()');

    if (currentCount > 1) {
      console.log('Threshold of over 1 reached.');
    } else {
      console.log('No threshold reached.');
    }
  });

  // const [count, setCount] = useStateWithCallbackInstant(0, currentCount => {
  //   console.log('render with instant callback.');

  //   if (currentCount > 1) {
  //     console.log('Threshold of over 1 reached.');
  //   } else {
  //     console.log('No threshold reached.');
  //   }
  // });

  const handleClick = () => {
    setCount(count + 1);
  };

  return (
    <div>
      {count}

      <button type="button" onClick={handleClick}>
        Increase
      </button>
    </div>
  );
};

export default App;

useStateWithCallbackLazy:

import * as React from 'react';
import { useStateWithCallbackLazy } from 'use-state-with-callback';

const App = () => {
  const [count, setCount] = useStateWithCallbackLazy(0);

  const handleClick = () => {
    setCount(count + 1, (currentCount) => {
      if (currentCount > 1) {
        console.log('Threshold of over 1 reached.');
      } else {
        console.log('No threshold reached.');
      }
    });
  };

  return (
    <div>
      <p>{count}</p>

      <button type="button" onClick={handleClick}>
        Increase
      </button>
    </div>
  );
};

export default App;

Pitfalls

• When a state update is called with the current value and optimized away, the callback is never called.
• useStateWithCallbackLazy calls the callback with the scope that existed before update, while this.setState callback can access the updated this.state and get something() computed values. This can't be fixed, but it's a problem for people who expect a drop-in replacement.
• When useStateWithCallbackLazy state is updated several times with batching (e.g. in an event handler), only the last update calls the callback.

Contribute

• git clone [email protected]:the-road-to-learn-react/use-state-with-callback.git
• cd use-state-with-callback
• npm install
• npm run test

More

• Publishing a Node Package to NPM
• Node.js Testing Setup
• React Testing Setup