What is the mental model for useEffect?
Think of it as 'after rendering, do this, and here is when to do it again.' The render produces the UI; the effect handles anything that reaches outside the component, like fetching or subscribing.
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More FAQs in What Is useEffect in React and How Does It Work?
useEffect runs a function after the component renders to perform side effects like data fetching, subscriptions, and DOM manipulation. It can optionally return a cleanup function that runs before the next effect or on unmount.
It controls when the effect runs. No array means it runs after every render. An empty array means it runs only on mount. An array with values means it runs when any of those values change.
Usually because you forgot the dependency array, or because you included a state variable that you update inside the effect. Each update triggers another run. Fix the dependency array so the effect only runs when intended.
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