For instance, a form component can include multiple input components, each managing its own state, while the parent container handles form submission and validation logic. This modular approach simplifies updates and feature extensions.

Example of componentDidMount in class component:
componentDidMount()
  fetch(‘https://api.example.com/data’)
    .then(response => response.json())
    .then(data => this.setState( data ))

Example of useState:
const [count, setCount] = useState(0);

setCount(count + 1)>Increment

Example of useEffect for data fetching:
useEffect(() =>
  fetch(‘https://api.example.com/data’)
  .then(response => response.json())
  .then(data => setData(data));
, []); // Empty dependency array ensures this runs only once after initial render

Examples of organized event handling include:

Dynamic parameters in routes, denoted by colon-prefixed segments (e.g., :id), enable rendering content based on URL variables. These parameters are accessible within components via hooks like useParams, facilitating data fetching and dynamic content display.

Summary: Redux is optimal for complex, large-scale state management requiring middleware and debugging, whereas Context API is ideal for simpler, localized state sharing with minimal setup.

Example of inline styles:

const buttonStyle = 
  backgroundColor: 'blue',
  color: 'white',
  padding: '10px 20px',
  borderRadius: '5px',
  cursor: 'pointer'
;

function StyledButton() 
  return <button style=buttonStyle>Click Me</button>;

Advantages of CSS Modules include:

1. Encapsulation: Styles are scoped locally, avoiding global conflicts.
2. Maintainability: Clear component-specific style files improve project organization.
3. Compatibility: Works seamlessly with existing CSS, allowing gradual adoption.

Example of styled-components:

import styled from 'styled-components';

const CustomButton = styled.button`
  background-color: #ff7f50;
  color: #fff;
  padding: 14px 28px;
  border-radius: 6px;
  border: none;
  cursor: pointer;
  font-size: 1rem;

  &:hover 
    background-color: #ff6347;
  
`;

function ReactStyledButton() 
  return <CustomButton>Learn More</CustomButton>;

import  render, screen, fireEvent  from '@testing-library/react';
import MyButton from './MyButton';

test('renders the button with correct label', () => 
  render();
  const buttonElement = screen.getByRole('button',  name: /Click Me/i );
  expect(buttonElement).toBeInTheDocument();
);

test('invokes callback when clicked', () => 
  const mockCallback = jest.fn();
  render( );
  const button = screen.getByRole('button',  name: /Submit/i );
  fireEvent.click(button);
  expect(mockCallback).toHaveBeenCalledTimes(1);
);

test('updates internal state on user input', () => 
  render( );
  const inputField = screen.getByPlaceholderText('Enter text');
  fireEvent.change(inputField,  target:  value: 'Hello World'  );
  expect(screen.getByDisplayValue('Hello World')).toBeInTheDocument();
);
 

React.memo: Wraps a functional component to prevent unnecessary re-rendering if its props haven’t changed.

useMemo: Caches the output of a function based on dependencies, avoiding recalculations unless dependencies change.

Effective monitoring involves tracking application performance, user interactions, and error logs to identify and resolve issues proactively.

For instance, a form component can include multiple input components, each managing its own state, while the parent container handles form submission and validation logic. This modular approach simplifies updates and feature extensions.

Example of componentDidMount in class component:
componentDidMount()
  fetch(‘https://api.example.com/data’)
    .then(response => response.json())
    .then(data => this.setState( data ))

Example of useState:
const [count, setCount] = useState(0);

setCount(count + 1)>Increment

Example of useEffect for data fetching:
useEffect(() =>
  fetch(‘https://api.example.com/data’)
  .then(response => response.json())
  .then(data => setData(data));
, []); // Empty dependency array ensures this runs only once after initial render

Examples of organized event handling include:

Dynamic parameters in routes, denoted by colon-prefixed segments (e.g., :id), enable rendering content based on URL variables. These parameters are accessible within components via hooks like useParams, facilitating data fetching and dynamic content display.

Summary: Redux is optimal for complex, large-scale state management requiring middleware and debugging, whereas Context API is ideal for simpler, localized state sharing with minimal setup.

Example of inline styles:

const buttonStyle = 
  backgroundColor: 'blue',
  color: 'white',
  padding: '10px 20px',
  borderRadius: '5px',
  cursor: 'pointer'
;

function StyledButton() 
  return <button style=buttonStyle>Click Me</button>;

Advantages of CSS Modules include:

1. Encapsulation: Styles are scoped locally, avoiding global conflicts.
2. Maintainability: Clear component-specific style files improve project organization.
3. Compatibility: Works seamlessly with existing CSS, allowing gradual adoption.

Example of styled-components:

import styled from 'styled-components';

const CustomButton = styled.button`
  background-color: #ff7f50;
  color: #fff;
  padding: 14px 28px;
  border-radius: 6px;
  border: none;
  cursor: pointer;
  font-size: 1rem;

  &:hover 
    background-color: #ff6347;
  
`;

function ReactStyledButton() 
  return <CustomButton>Learn More</CustomButton>;

import  render, screen, fireEvent  from '@testing-library/react';
import MyButton from './MyButton';

test('renders the button with correct label', () => 
  render();
  const buttonElement = screen.getByRole('button',  name: /Click Me/i );
  expect(buttonElement).toBeInTheDocument();
);

test('invokes callback when clicked', () => 
  const mockCallback = jest.fn();
  render( );
  const button = screen.getByRole('button',  name: /Submit/i );
  fireEvent.click(button);
  expect(mockCallback).toHaveBeenCalledTimes(1);
);

test('updates internal state on user input', () => 
  render( );
  const inputField = screen.getByPlaceholderText('Enter text');
  fireEvent.change(inputField,  target:  value: 'Hello World'  );
  expect(screen.getByDisplayValue('Hello World')).toBeInTheDocument();
);
 

React.memo: Wraps a functional component to prevent unnecessary re-rendering if its props haven’t changed.

useMemo: Caches the output of a function based on dependencies, avoiding recalculations unless dependencies change.

Effective monitoring involves tracking application performance, user interactions, and error logs to identify and resolve issues proactively.