What Must The Useeffect Function For An Async Function Return In Order To Avoid React Hook Warnings In JavaScript?

The warning you mentioned occurs when the useEffect hook doesn’t return a cleanup function or anything. The cleanup function is necessary to clean up any resources or subscriptions created within the effect.

In the case of an async function in useEffect, you cannot directly return an async function as the cleanup function. Instead, you need to create an intermediate function and return it as the cleanup function. Here’s an example:

useEffect(() => {
  const fetchData = async () => {
    try {
      const response = await fetch('https://example.com/api/data');
      const data = await response.json();
      // Perform further operations with the data
    } catch(error) {
      // Handle error


  return () => {
    // Clean up any resources or subscriptions here
}, []);

In this example, the fetchData function is an async function responsible for fetching data. It’s called within the effect, and an empty dependency array [] is passed to ensure it runs only once. Finally, the cleanup function is defined and returned, which can be used to clean up any resources when the component unmounts or when dependencies change.

Make sure you include a cleanup function or return nothing in your useEffect hook to resolve the warning.

About the Author Rex

I'm a passionate tech blogger with an insatiable love for programming! From my early days tinkering with code, I've delved into web dev, mobile apps, and AI. Sharing insights and tutorials with the world is my joy, connecting me to a global community of like-minded tech enthusiasts. Python holds a special place in my heart, but I embrace all challenges. Constantly learning, I attend tech conferences, contribute to open-source projects, and engage in code review sessions. My ultimate goal is to inspire the next generation of developers and contribute positively to the ever-evolving tech landscape. Let's code together!