React Core Concepts

React is a popular JavaScript library for building user interfaces, especially for single-page applications. Its focus on a component-based architecture makes development more modular and reusable. Let’s explore the core concepts that make React powerful and efficient.

1. Components

• Definition: Components are the building blocks of a React application. They represent parts of the user interface.
• Types:
  • Functional Components: Simple functions that return JSX.
  • Class Components: ES6 classes extending React.Component (less common in modern React due to hooks).
• Reusable: Components can be reused across the application.

2. JSX (JavaScript XML)

• What it is: A syntax extension that allows writing HTML-like code in JavaScript.
• How it works: JSX is compiled into JavaScript functions by tools like Babel.
• Example:

const Greeting = () => <h1>Hello, World!</h1>;

3. State and Props

• State:
  • Internal data managed within a component.
  • Mutable and used to track component behavior.
  • Example:

const [count, setCount] = React.useState(0);

• Props:
  • Short for "properties."
  • Data passed from a parent component to a child component.
  • Immutable.

4. Lifecycle Methods (for Class Components)

• Methods that let you hook into component creation, updating, and destruction phases.
• Examples: componentDidMount, componentDidUpdate, componentWillUnmount.

With functional components and hooks, lifecycle methods are replaced by hook usage like useEffect.

5. Hooks

• Introduced in React 16.8 to manage state and side effects in functional components.
• Common hooks:
  • useState: Manages state.
  • useEffect: Handles side effects like API calls.
  • useContext: Accesses context values.
• Example:

const [count, setCount] = useState(0);
useEffect(() => {
  console.log(`Count is ${count}`);
}, [count]);

6. Virtual DOM

• React uses a virtual DOM to efficiently update and render the user interface.
• Changes are calculated in the virtual DOM and then applied to the real DOM, minimizing performance overhead.

7. React Router

• Used for navigation in single-page applications.
• Allows for client-side routing and dynamic rendering of components.

8. Context API

• A way to share state across components without prop drilling.
• Example:

const ThemeContext = React.createContext();

React simplifies the process of building scalable and interactive UIs. By understanding these core concepts, you can create efficient and maintainable applications.