React Useeffect — Free React Tutorial
Learn React Useeffect in React with a free, beginner-friendly tutorial, examples and practice for Indian students on Syllab.in.
TL;DR: Learn React Useeffect in React with a free, beginner-friendly tutorial, examples and practice for Indian students on Syllab.in.
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React Useeffect in React
The `useEffect` hook lets you perform side effects in functional components. Side effects are actions that interact with the outside world: fetching data, setting up timers, updating the document title, or subscribing to events. Side effects should not happen during rendering; they happen after the component renders. The `useEffect` hook runs after React updates the DOM. You can run effects after every render or only when dependencies change.
Every `useEffect` call can have a dependency array as the second argument. If the array is omitted, the effect runs after every render. If the array is empty `[]`, the effect runs once when the component mounts. If the array contains values, the effect runs only when those values change. React compares the dependencies using strict equality, so include all values from the component scope that the effect uses.
To clean up after side effects (like unsubscribing or canceling timers), return a cleanup function from `useEffect`. The cleanup function runs before the effect runs again and when the component unmounts. This prevents memory leaks and ensures your app doesn't perform duplicate operations.
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