In React, class components are a type of component that allow you to define a component as a class instead of a function. Class components are more powerful than functional components, because they allow you to define state and lifecycle methods.
Here’s an example of a simple class component:
import React, { Component } from 'react';
class MyComponent extends Component {
render() {
return (
<div>
<h1>Hello, world!</h1>
</div>
);
}
}
export default MyComponent;
In this example, we’re defining a class component called MyComponent that extends the Component class from the react module. The component has a render method that returns some JSX code, which in this case is a simple <h1> tag that says “Hello, world!”.
Class components can also define state, which is an object that represents the internal data of the component. Here’s an example that shows how to define and use state in a class component:
import React, { Component } from 'react';
class Counter extends Component {
state = {
count: 0
};
handleClick = () => {
this.setState({ count: this.state.count + 1 });
};
render() {
return (
<div>
<p>Count: {this.state.count}</p>
<button onClick={this.handleClick}>Increment</button>
</div>
);
}
}
export default Counter;
In this example, we’re defining a class component called Counter that maintains a count in its state and renders a button that increments the count when clicked. The handleClick method updates the state using the setState method, which causes the component to re-render with the updated count.
Overall, class components provide a powerful way to define complex and interactive user interfaces in React, and allow you to use state and lifecycle methods to manage the component’s internal data and behavior.
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