What Are React Components in React?

This article provides a clear overview of React components, the essential building blocks of any React application. You will learn what components are, the differences between functional and class components, and how they use props and state to build dynamic, reusable user interfaces.

Understanding React Components

In React, a component is a self-contained, reusable piece of code that represents a part of the user interface (UI). Think of components as Lego bricks; you can combine them in various ways to build complex structures.

Components let you split the UI into independent, reusable pieces, allowing you to think about each piece in isolation. Legibility, maintainability, and scalability are the primary benefits of using a component-based architecture.

Types of React Components

There are two main types of components in React:

1. Functional Components

Functional components are the modern standard for writing React code. They are simply JavaScript functions that accept “props” (properties) as an argument and return React elements (written in JSX).

With the introduction of React Hooks, functional components can manage local state, handle side effects, and use other React features that were previously only available in class components.

function Welcome(props) {
  return <h1>Hello, {props.name}</h1>;
}

2. Class Components

Class components are ES6 classes that extend from React.Component. They require a render() method to return JSX. While class components were once the only way to manage state and lifecycle methods, they are now considered legacy code. Modern React projects favor functional components.

class Welcome extends React.Component {
  render() {
    return <h1>Hello, {this.props.name}</h1>;
  }
}

How Components Work: Props and State

To make components dynamic and interactive, React utilizes two types of data: Props and State.

• Props (Properties): Props are read-only inputs passed to a component from its parent. They allow you to pass data down the component tree. A component can never modify its own props.
• State: State is an internal, mutable data storage local to the component. When state data changes, the component automatically re-renders to reflect the new data in the UI.

Component Reusability and Composition

One of React’s greatest strengths is component composition. You can nest components inside other components, allowing you to build complex pages from simple, discrete parts. For example, a App component might contain a Header component, a Sidebar component, and a Footer component, each containing smaller components like buttons and text inputs.