42. What is the composition pattern in React?
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The Composition Pattern in React is a design principle that involves combining smaller, reusable components to build more complex UIs. This approach is preferred over inheritance for creating complex user interfaces.


Key Concepts of Composition

Composition allows for building flexible and reusable components. There are two main ways to implement composition in React:

  • Passing Components as Children: Nest components by passing them as children to create structured layouts.
  • Passing Components as Props: Provide components as props to dynamically render different UIs, offering more flexibility.

Example: Passing Components as Children:

function Dialog(props) {
  return <div className="dialog">{props.children}</div>;
}

function WelcomeDialog() {
  return (
    <Dialog>
      <h1>Welcome</h1>
      <p>Thank you for visiting our spacecraft!</p>
    </Dialog>
  );
}


Example: Passing Components as Props:

function SplitPane(props) {
  return (
    <div className="split-pane">
      <div className="split-pane-left">{props.left}</div>
      <div className="split-pane-right">{props.right}</div>
    </div>
  );
}

function App() {
  return <SplitPane left={<Contacts />} right={<Chat />} />;
}

Benefits of Composition

  • Reusability: Smaller components can be reused in different parts of the app.
  • Maintainability: Smaller pieces are easier to test, debug, and maintain.
  • Flexibility: Components can be assembled in various combinations to support different UI needs.

When to Use Composition

  • When you need to create complex UIs from smaller, reusable pieces.
  • When you want to avoid the complexity and rigidity of inheritance.

Conclusion

In summary, the composition pattern in React promotes building complex user interfaces by combining smaller, reusable components. It offers reusability, maintainability, and flexibility, making it a preferred approach for creating scalable React applications.

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