What are class components?
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A class component requires you to extend from React.Component and create a render function that returns a React element.
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Class components are based on ES6 classes and can have their own state and lifecycle methods.
Scenario Questions
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How would you turn a simple counter widget into a class component?
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What happens if you forget to bind an event handler in a class component?
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Where and how do you initialize state in a class component's constructor?
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We fetch data in componentDidMount, but the component leaks memory when unmounted. How would you fix it?
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Why does a class component re‑render when setState is called with the same value, and how can you avoid unnecessary renders?
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If a parent passes a new prop that doesn't affect rendering, what can you do to optimise the class component?
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Our dashboard has dozens of class components with complex lifecycle logic. How would you refactor them for better maintainability and testability?
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Discuss the trade‑offs between using shouldComponentUpdate and extending PureComponent in a large list rendering scenario.
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When doing server‑side rendering, what extra considerations do class components introduce compared to functional components with hooks?
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Our codebase is 80% class components and we plan to migrate to hooks over the next few years. How would you design a migration strategy that minimizes risk and keeps teams productive?
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How would you create a shared base class for common behavior across many class components while avoiding tight coupling?
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What architectural implications arise when mixing class components and functional components in a large app, and how would you enforce consistency?
Follow-up Questions
- ❓Can you show a quick code snippet for that?
- ❓What would you change if you needed to add new props?
- ❓How does this affect testing the component?