Counter App

Two Test suites

3 As

Hooks
- Hooks are a new addition in React 16.8. They let you use state and other React features without writing a class. Hooks are functions that let you "hook into" React state and lifecycle features from function components. They do not work inside classes — they let you use React without classes. Instead, Hooks offer a more direct API to the React concepts you already know: props, state, context, refs, and lifecycle. This will not fundamentally change how you write React applications; it will, however, enable some new features you might find helpful.

Other React features that can be used with Hooks include

Effects: The Effect Hook, useEffect, adds the ability to perform side effects from a function component. It serves the same purpose as componentDidMount, componentDidUpdate, and componentWillUnmount in React classes.
Context: The Context Hook, useContext, lets you subscribe to React context without introducing nesting.
Reducer: The Reducer Hook, useReducer, is usually preferable to useState when you have complex state logic that involves multiple sub-values.
Ref: The Ref Hook, useRef, can be used to access DOM nodes or React elements created in the render method.
Memo: The Memo Hook, useMemo, returns a memoized value, helping you avoid expensive calculations on every render.
Callback: The Callback Hook, useCallback, returns a memoized version of the callback that only changes if one of the dependencies has changed.
Imperative Handle: The Imperative Handle Hook, useImperativeHandle, customizes the instance value that is exposed to parent components when using ref.
Layout Effect: The Layout Effect Hook, useLayoutEffect, runs synchronously immediately after React has performed all DOM mutations. This can be useful if you need to make layout measurements.
Debug Value: The Debug Value Hook, useDebugValue, can be used to display a label for custom hooks in React DevTools.