What is useEffect Hook? What are dependency arrays wrt useEffect?

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useEffect Hook is a built-in hook in React that allows you to perform side effects in functional components.

useEffect Hook is used to handle side effects in functional components, such as fetching data, subscribing to events, or manipulating the DOM.
It takes two arguments: a function that represents the side effect, and an optional dependency array.
The function passed to useEffect will be executed after every render, unless the dependency array is provided.
The dependency array is used to specify the values that the effect depends on. If any of the values in the dependency array change, the effect will be re-run.
If the dependency array is empty, the effect will only run once, after the initial render.
If the dependency array is not provided, the effect will run after every render, causing potential performance issues.
Example: useEffect(() => { console.log('Effect ran'); }, []); // Runs only once after the initial render
Example: useEffect(() => { console.log('Effect ran'); }, [count]); // Runs whenever the 'count' value changes

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