How do you handle side effects in React?

How do you handle side effects in React?

A side effect is an operation that affects something outside the scope of the component, such as making an API call, setting a timer, or updating the DOM directly.

Handling side effects is crucial in React because they can cause unintended consequences, like infinite loops or memory leaks.

In this explanation, we'll dive into how to handle side effects in React.

Key Components to Handle Side Effects in React:

  • Side effects: Operations that affect something outside the component's scope.
  • UseEffect Hook: A built-in React hook that allows you to run side effects in functional components.
  • Cleanup functions: Functions that clean up after side effects to prevent memory leak

Step-by-Step Explanation:

  1. Identify the side effect: Determine what operation is causing the side effect, such as making an API call or setting a timer.
  2. Use the useEffect hook: Wrap the side effect in a useEffect hook to ensure it runs only when necessary.
  3. Specify dependencies: Provide an array of dependencies that trigger the side effect. If the dependencies change, the side effect will re-run.
  4. Return a cleanup function: Return a function that cleans up after the side effect to prevent memory leaks.


Suppose we want to fetch data from an API when a component mounts.

We can use the useEffect hook to handle this side effect:

import { useState, useEffect } from 'react';

function MyComponent() {
  const [data, setData] = useState([]);

  useEffect(() => {
      .then(response => response.json())
      .then(data => setData(data));
    return () => {
      // Cleanup function to cancel the API requestconsole.log('Cleaning up API request');
  }, []); // Empty dependency array means the effect runs only once

  return <div>Data: {data}</div>;

In this example, the useEffect hook fetches data from the API when the component mounts and sets the data state.

The cleanup function logs a message to the console when the component is unmounted.

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