If you have started to use React’s useState hook for your application, you may be missing a callback function, because only the initial state can be passed to the hook. In React class components, the setState method offers an optional second argument to pass a callback function. However, this second argument isn’t available for React’s useState hook. If you are moving from React class components to function components, this may be a concern for you. In this tutorial, I want to explain you how to implement it.

Note: If you are just looking for an out of the box solution, check out this custom useState hook with callback function. That’s what you are going to implement in this tutorial anyway. I will show how this works below as well.

React useState Callback

In React Function Components with Hooks, you can implement a callback function for anything using the useEffect hook. For instance, if you want to have a callback function for a state change, you can make the useEffect hook dependent on this state:

import React from 'react';

const App = () => {
  const [count, setCount] = React.useState(0);

  React.useEffect(() => {
    if (count > 1) {
      console.log('Threshold of over 1 reached.');
    } else {
      console.log('No threshold reached.');
    }
  }, [count]);

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

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

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

export default App;

The function you pass to the useEffect hook is your callback function which runs after the provided state changes from the useState hook’s second argument. If you perform changes in this callback function that should be reflected in your component’s rendered output, you may want to use useLayoutEffect instead of useEffect.

If you are looking for an out of the box solution, check out this custom hook that works like useState but accepts as second parameter as callback function:

import React from 'react';

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

const App = () => {
  const [count, setCount] = useStateWithCallback(0, count => {
    if (count > 1) {
      console.log('Threshold of over 1 reached.');
    } else {
      console.log('No threshold reached.');
    }
  });

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

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

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

export default App;

The custom hook can be installed via npm install use-state-with-callback. At the end, the React team decided consciously against a second argument for useState for providing a callback function, because useEffect or useLayoutEffect can be used instead. However, if you are lazy, you can use the custom hook to get the same effect as setState from React class components.

React useState with Lazy Callback Function

If you want to have a lazy executable function instead, you can use the library as well:

import 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;

This way, you can decide when to use the second argument for the callback function and you can decide for each case what the callback function should do specifically.