👀 Views: 29 💬 Answers: 1 📅 Created: 2025-06-17

react useEffect hooks JavaScript

I've been banging my head against this for hours. I'm performance testing and I'm stuck on something that should probably be simple... I'm having trouble with I'm working with an scenario with the cleanup function in a React component using the `useEffect` hook. My goal is to reset the state of a component when it unmounts, but I'm seeing that the state isn't resetting as expected. Here's a simplified version of my component: ```javascript import React, { useEffect, useState } from 'react'; const TimerComponent = () => { const [time, setTime] = useState(0); const [isActive, setIsActive] = useState(false); useEffect(() => { let timer; if (isActive) { timer = setInterval(() => { setTime(prevTime => prevTime + 1); }, 1000); } return () => { clearInterval(timer); setTime(0); // Trying to reset time on unmount }; }, [isActive]); return ( <div> <h1>{time} seconds</h1> <button onClick={() => setIsActive(!isActive)}>{isActive ? 'Pause' : 'Start'}</button> </div> ); }; ``` When I start the timer and then navigate away from this component, I expect `time` to reset to `0` due to the cleanup function. However, when I return to the component, the timer resumes from the last value instead of starting over. The cleanup function seems to be executing correctly, but I suspect that the state might be persisting in some unexpected way. I'm using React 17 and functional components. I've tried various approaches, like manually resetting the state in the component's main function, but that hasn't resolved the question. What am I missing? Any insights would be greatly appreciated! I'm open to any suggestions. This issue appeared after updating to Javascript latest. Am I missing something obvious? Any help would be greatly appreciated! I'm working in a macOS environment. Has anyone else encountered this?