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How to define a new component in ReactJS

Getting Started

If you're new to the world of programming, you may have heard of ReactJS, a popular JavaScript library for building user interfaces. One of the key concepts in React is the component. But what exactly is a component and how do you define one? Let's dive in.

Understanding Components

Think of components as the building blocks of your React application. Just like how a house is built with individual bricks, a React application is built with individual components. Each component represents a part of the user interface (UI), and when combined, they form the complete UI of your application.

How to Define a Component

There are two types of components in React: function components and class components. Although there are some differences between the two, they serve the same purpose - to render UI.

Function Components

Function components, as the name suggests, are simply JavaScript functions. They take in properties (props) as an argument and return what should be rendered.

Let's say we want to create a function component that renders a button. Here's how we could do it:

function Button(props) {
  return (

In this example, Button is a function component. It takes props as an argument and returns a button element. The content of the button is determined by props.label.

Class Components

On the other hand, class components are ES6 classes. They must have a render method which returns what should be displayed on the screen.

Let's create the same button component as a class component:

class Button extends React.Component {
  render() {
    return (

In this case, Button is an ES6 class extending React.Component. The render method returns a button element, and the content of the button is determined by this.props.label.

Utilizing Components

Now that we've defined our Button component, let's see how we can use it in our application.

function App() {
  return (
      <Button label="Click me!" />

In this example, we've defined an App component that uses our Button component. The Button component is passed a prop label with the value "Click me!". This value is what will be displayed on the button.


Learning to define components in ReactJS is like learning to use new Lego blocks. With these blocks, you can create anything you want, from a simple single-page application to a complex web app. The more you practice, the more comfortable you'll become with building these blocks and seeing how they all fit together.

Just remember, the key to mastering ReactJS is understanding and effectively using components. They're the heart and soul of any React application, and the more proficient you become in defining and using them, the more powerful your React applications will be. So keep practicing, keep building, and most importantly, have fun with it!