👀 Views: 91 💬 Answers: 1 📅 Created: 2025-06-06

react useEffect event-listener JavaScript

I'm facing an issue with the cleanup of event listeners in a React functional component using the `useEffect` hook. I have a component that listens for mouse movements and updates the state accordingly. However, when the component unmounts, I expect the event listener to be removed, but it seems like it continues to run, causing memory leaks and unexpected behavior when the component is re-mounted. Here's a simplified version of my code: ```javascript import React, { useEffect, useState } from 'react'; const MouseTracker = () => { const [mousePosition, setMousePosition] = useState({ x: 0, y: 0 }); useEffect(() => { const handleMouseMove = (event) => { setMousePosition({ x: event.clientX, y: event.clientY }); }; window.addEventListener('mousemove', handleMouseMove); // Cleanup function return () => { window.removeEventListener('mousemove', handleMouseMove); }; }, []); return <div>Mouse Position: {`(${mousePosition.x}, ${mousePosition.y})`}</div>; }; export default MouseTracker; ``` I've tried adding console logs inside the cleanup function to see if it's actually being called, and it seems to log when the component unmounts, but when I re-mount the component, the event listener seems to still be active because the state updates are firing again and causing the position to be logged multiple times. I’m using React 17.0.2. Is there something I’m missing in the hook's lifecycle management, or could there be another reason why the event listener isn’t being cleaned up as expected? Any insights would be appreciated!