-
What is React?
- A JavaScript library for building user interfaces, particularly single-page applications.
- Developed and maintained by Facebook.
- Enables the creation of reusable UI components.
Core Concepts
1. Components
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Functional Components: JavaScript functions that return React elements. Can use hooks for state and lifecycle features.
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Class Components: ES6 classes that extend
React.Component
. Used for more complex logic and state management before hooks were introduced.
2. JSX (JavaScript XML)
- A syntax extension that allows you to write HTML-like code within JavaScript.
- JSX is transformed into React elements.
- Example:
const element = <h1>Hello, world!</h1>;
3. Props
- Short for "properties," props are used to pass data from parent components to child components.
- Props are read-only and help in making components reusable.
- Example:
<MyComponent title="Welcome" />
4. State
- A built-in object that allows components to create and manage their own data.
- State changes trigger re-renders of the component.
- Use the
useState
hook for functional components:
const [count, setCount] = useState(0);
5. Lifecycle Methods
- Class components have lifecycle methods (e.g.,
componentDidMount
, componentDidUpdate
, componentWillUnmount
) to manage side effects.
- In functional components, use the
useEffect
hook to achieve similar functionality.
6. Event Handling
- React uses camelCase syntax for events.
- Events can be passed as props to components.
- Example:
<button onClick={handleClick}>Click me</button>
Advanced Concepts
1. Hooks
- Functions that let you use state and other React features in functional components.
- Common hooks include:
-
useState()
: For state management.
-
useEffect()
: For side effects (data fetching, subscriptions).
-
useContext()
: For accessing context.
2. Context API
- A way to share values (like themes or user information) between components without having to pass props down manually at every level.
- Create a context with
React.createContext()
and use Provider
and Consumer
.
3. React Router
- A library for routing in React applications.
- Allows for navigation between different views and supports nested routes.
- Example:
<BrowserRouter>
<Route path="/about" component={About} />
</BrowserRouter>
4. State Management Libraries
- For larger applications, consider using state management libraries like:
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Redux: Predictable state container for JavaScript apps.
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MobX: Simple, scalable state management.
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Recoil: For managing state in React applications.
Performance Optimization
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Memoization: Use
React.memo
for functional components to prevent unnecessary re-renders.
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useMemo & useCallback: Hooks to memoize values and functions, improving performance in complex components.
Testing
- Use libraries like:
-
Jest: A JavaScript testing framework.
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React Testing Library: For testing React components with a focus on user interactions.
Conclusion
- React is a powerful library that promotes a component-based architecture, making it easier to build and maintain user interfaces.
- Understanding its core concepts, hooks, and best practices is essential for effective React development.
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