What Are Hooks in React JS?

• Hooks are a new feature introduced in React JS that allow developers to use state and other React features without writing a class component. Prior to hooks, these features were only available to class components, which made it difficult to reuse stateful logic and to organize complex components.

• Hooks provide a way to reuse stateful logic between components by allowing developers to extract logic into reusable functions, called hooks. Hooks also simplify component code by reducing the number of class components and providing an easier-to-understand syntax for managing state and side effects.

• There are several built-in hooks in React, including useState, useEffect, useContext, and useReducer, among others. Each hook provides a specific functionality that can be used to manage state, handle side effects, and interact with the React context.

• Hooks were introduced in React 16.8 as a way to simplify the state management and logic in functional components.

• Hooks are just plain JavaScript functions that use special syntax and must follow certain rules. They can only be called at the top level of a component or other hook, and can't be called conditionally or in loops. Hooks always return an array of values, with the first item being the state value and the second item being a function to update the state value.

• useState(): This is the most commonly used hook in React JS. It allows you to add state to functional components by returning a pair of values: the current state value and a function to update that value. You can use the same useState() hook multiple times in a component to manage multiple state values.

• useEffect(): This hook is used to manage side effects in a component, such as fetching data from an API or subscribing to an event. It runs after every render of the component, and can be used to add or remove event listeners, start or stop timers, or update the document title.

• useContext(): This hook allows you to pass data down the component tree without using props. It creates a context object that can be shared between components, and a useContext() hook that can be used to access that context value in any descendant component.

• useReducer(): This hook is similar to useState(), but allows you to manage more complex state values with a reducer function. It takes an initial state value and a reducer function as arguments, and returns the current state value and a dispatch function to update that state.

• useCallback(): This hook is used to memoize a function, so that it only gets recreated if its dependencies change. This can be useful for optimizing performance in components that rely on expensive computations or API calls.

• Overall, hooks have made it easier to write reusable and maintainable code in React, especially for functional components that previously had limited access to the built-in React features.