Hooks are a new addition in React 16.8. They let you use state and other React features without writing a class.
The Effect Hook lets you perform side effects in function components.
This article assumes you already know the basics of useEffect, but as a reminder: useEffect() mimics the behavior of componentDidMount, componentDidUpdate and componentWillUnmount life cycle methods from class components. UseEffect takes two arguments, one call back function (our effect) and a dependency array. This hook watches for changes and every time one of the dependencies changes, the effect runs again. If we want it to run just once, we leave the array empty.Read more