What are Components & their types in ReactJs

Components are the building blocks of ReactJS applications. A component is a self-contained block of code that encapsulates functionality and can be reused throughout an application. ReactJS provides a powerful and flexible way to create components, which makes it easy to create complex and dynamic user interfaces.

There are two main types of components in ReactJS:

• Functional Components 
• Class Components.

Functional Components

Functional components are the simplest type of component in ReactJS. They are also known as "stateless" components because they don't have any internal state of their own. Functional components are simply JavaScript functions that return a JSX expression, which describes the content of the component. Here's an example of a simple functional component:

function Greeting(props) {

  return <h1>Hello, {props.name}!</h1>;

}

In this example, the Greeting component takes a prop called name and returns a JSX expression that displays a greeting with the value of the name prop.

Functional components are easy to write and understand, and they are typically used for simple, presentational components that don't need to manage any internal state.

Class Components

Class components are a more powerful type of component in ReactJS. They are also known as "stateful" components because they have their own internal state that can be updated and managed. Class components are defined as JavaScript classes that extend React. Component class and define a render() method, which returns a JSX expression. Here's an example of a simple class component:

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()}>Click me</button>

      </div>

    );

  }

}

In this example, the Counter component defines an internal state with a count property, and a handleClick() method that updates the state when the button is clicked. The render() method returns a JSX expression that displays the current count value and a button that triggers the handleClick() method.

Class components are more complex than functional components, but they are also more flexible and powerful. They are typically used for more complex components that need to manage internal state or handle user interactions.

In addition to these main types of components, there are also Higher-Order Components (HOCs) and Render Props, which are advanced techniques for creating reusable components in ReactJS. HOCs are functions that take a component as an argument and return a new component with enhanced functionality, while Render Props are a pattern for sharing code between components using a prop that is a function.

In conclusion, components are a key concept in ReactJS, and there are two main types of components: Functional Components and Class Components. Functional components are simple and stateless, while class components are more powerful and can manage their own internal state. Higher-Order Components and Render Props are also advanced techniques for creating reusable components in ReactJS. By understanding these different types of components, you can create powerful and flexible user interfaces in your ReactJS applications.

To learn ReactJS, you can start with the ReactJS tutorial. This tutorial will introduce you to the basics of React, including components, JSX syntax, and state management.