ReactJS Anti Pattern　~Not Cleaning Up Side-Effects~

・Leaving side-effects like subscriptions, timers, or event listeners uncleared can cause memory leaks and unexpected behaviors.This is especially problematic in components that are frequently mounted and unmounted. // Anti-pattern React . useEffect (() => { const timer = setInterval (() => { console . log ( " Running... " ); }, 1000 ); }, []); Always return a cleanup function in useEffect to clean up side-effects when the component unmounts. // Correct approach React . useEffect (() => { const timer = setInterval (() => { console . log ( " Running... " ); }, 1000 ); return () => clearInterval ( timer ); }, []);