Optimizing React Performance: Preventing Excessive Fires of useEffect

That's a common challenge that many React developers face, especially when they are new to React and its useEffect hook. It's important to understand the purpose of the dependency array in the useEffect hook and how it affects the behavior of the effect.

The dependency array in useEffect is used to specify the values that the effect depends on. React tracks these dependencies, and whenever any of the dependencies change, the effect is re-executed. If the dependency array is omitted, the effect runs after every render.

While it's generally a good practice to include all relevant dependencies in the dependency array to ensure that the effect runs when the expected values change, there are cases where adding every reactive value to the dependency array can lead to performance issues.

Let's check the code below.

function ChatRoom({ roomId }) {
  const [message, setMessage] = useState('');

  function createOptions() {
    return {
      serverUrl: 'https://localhost:1234',
      roomId: roomId
    };
  }

 useEffect(() => {
    const options = createOptions();
    const connection = createConnection();
    connection.connect();
    return () => connection.disconnect();
  }, [createOptions]); // 🔴 Problem: This dependency changes on every render
  // ...

Let's see how useCallback hook can solve this challenge. Check the code snippet below:

function ChatRoom({ roomId }) {
  const [message, setMessage] = useState('');

  const createOptions = useCallback(() => {
    return {
      serverUrl: 'https://localhost:1234',
      roomId: roomId
    };
  }, [roomId]); // ✅ Only changes when roomId changes

  useEffect(() => {
    const options = createOptions();
    const connection = createConnection();
    connection.connect();
    return () => connection.disconnect();
  }, [createOptions]); // ✅ Only changes when createOptions changes

In this example, createOptions is memoized using useCallback. The createOptions function is passed as a dependency to the useEffect hook. Since createOptions will remain the same between re-renders, the effect will only be triggered if any of the other dependencies specified in the dependency array change. This prevents the effect from being re-executed unnecessarily, optimizing performance.

By using useCallback to memoize functions and specifying dependencies in useEffect, you can fine-tune when the effect should run, minimizing unnecessary computations and improving overall performance in your React components.