React is a powerful library for building user interfaces, primarily for single-page applications, where you can update and render efficiently in response to data changes. Here’s a comprehensive guide, diving into several aspects of React with exercises.
React Components have a lifecycle, and it's crucial to understand the different lifecycle methods. A common exercise is to create a component and log messages in each lifecycle method.
class LifecycleComponent extends React.Component {
constructor(props) {
super(props);
console.log('Constructor');
}
componentDidMount() {
console.log('Component Did Mount');
}
componentDidUpdate() {
console.log('Component Did Update');
}
componentWillUnmount() {
console.log('Component Will Unmount');
}
render() {
console.log('Render');
return <div>Hello, React!</div>;
}
}
Create different components and observe the order of lifecycle methods invoked during mounting, updating, and unmounting.
State is internal to a component, while props are external. Understanding the interaction between state and props is crucial.
class StatePropsComponent extends React.Component {
constructor(props) {
super(props);
this.state = {
count: 0,
};
}
incrementCount = () => {
this.setState({ count: this.state.count + 1 });
};
render() {
return (
<div>
<p>{this.props.message}</p>
<p>Count: {this.state.count}</p>
<button onClick={this.incrementCount}>Increment</button>
</div>
);
}
}
Create a component that receives props and has state, then modify the state based on user interaction and observe the component re-render.
Conditional rendering is a technique to render different UI markup based on certain conditions.
function ConditionalComponent({ isLoggedIn }) {
return <div>{isLoggedIn ? <p>Welcome back!</p> : <p>Please sign in.</p>}</div>;
}
Create components that use conditional rendering to display different messages or elements based on state or props.
React elements can have event listeners attached to handle user interactions.
function ButtonComponent() {
const handleClick = () => {
alert('Button Clicked!');
};
return <button onClick={handleClick}>Click me</button>;
}
Create a component with different event listeners and observe how they can be used to modify state or props.
Rendering lists is a common task, and React requires keys to identify each list item uniquely.
function ListComponent({ items }) {
return (
<ul>
{items.map(item => (
<li key={item.id}>{item.name}</li>
))}
</ul>
);
}
Create a component that renders a list of items with unique keys and try modifying the list items to observe re-renders.
Handling forms involves maintaining form control values in state and handling submission.
class FormComponent extends React.Component {
constructor(props) {
super(props);
this.state = {
value: '',
};
}
handleChange = event => {
this.setState({ value: event.target.value });
};
handleSubmit = event => {
alert('Submitted: ' + this.state.value);
event.preventDefault();
};
render() {
return (
<form onSubmit={this.handleSubmit}>
<label>
Name:
<input type="text" value={this.state.value} onChange={this.handleChange} />
</label>
<button type="submit">Submit</button>
</form>
);
}
}
Create a form with different form controls, manage their state, and handle their submission.
The Context API allows passing data through the component tree without having to pass props down manually at every level.
const ThemeContext = React.createContext('light');
class ContextComponent extends React.Component {
render() {
return (
<ThemeContext.Provider value="dark">
<ThemedComponent />
</ThemeContext.Provider>
);
}
}
function ThemedComponent() {
const theme = React.useContext(ThemeContext);
return <div>Theme is {theme}</div>;
}
Create a component that uses the Context API to pass data to its children, then access this data from a child component.
Hooks are functions that let developers use state and other React features in functional components.
function CounterComponent() {
const [count, setCount] = React.useState(0);
return (
<div>
<p>You clicked {count} times</p>
<button onClick={() => setCount(count + 1)}>Click me</button>
</div>
);
}
Create functional components and use different hooks like `useState`, `useEffect`, and `useContext` to add state and side effects to them.
HOC is a function that takes a component and returns a new component with additional props or behaviors.
function withHover(Component) {
return class extends React.Component {
state = { hover: false };
toggleHover = () => this.setState({ hover: !this.state.hover });
render() {
return (
<div onMouseOver={this.toggleHover} onMouseOut={this.toggleHover}>
<Component {...this.props} hover={this.state.hover} />
</div>
);
}
};
}
const EnhancedComponent = withHover(OriginalComponent);
Create an HOC that modifies the behavior or appearance of the wrapped component and use it to enhance a component.
React Exercises are practical methods to understand the working, integration, and manipulation of various concepts like Lifecycle methods, State, Props, Context API, Hooks, etc., in React. Regular practice with different exercises like the ones listed above can help in building a solid understanding of React. This guide provides a fundamental understanding and practical examples for different aspects of React. To gain mastery, continuously build projects, experiment with different features, and explore advanced topics like Redux for state management, and React Router for navigation.
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