What is Components in React js

• Components are the building blocks of ReactJS applications. A component in ReactJS is a self-contained piece of code that defines a part of a user interface. It can be a button, a form, a header, or any other UI element. A component can be reused multiple times in the same application, making it a powerful and efficient way to build complex user interfaces.

• In ReactJS, there are two types of components: functional and class components.

• Functional components are simple functions that return a React element. They are often used for simple UI elements that don't require state or lifecycle methods. Here's an example of a functional component that renders a simple button:

function MyButton(props) {

    return <button>{props.label}</button>;

}

• Class components are more powerful than functional components, as they can have state and lifecycle methods. They are used for more complex UI elements that need to manage their own state or respond to changes in the application. Here's an example of a class component that renders a simple counter:

class Counter extends React.Component {

    constructor(props) {

        super(props);

        this.state = { count: 0 };

    }

    handleClick() {

        this.setState({ count: this.state.count + 1 });

    }

    render() {

        return (

            <div>

                <p>Count: {this.state.count}</p>

                <button onClick={this.handleClick.bind(this)}>Increment</button>

            </div>

        );

    }

}

• Both functional and class components can be used to create complex user interfaces in ReactJS applications. They can be composed together to create a hierarchy of components, with each component being responsible for rendering a specific part of the UI.