What is React?
It's a JavaScript library for building user interfaces. It allows developers to create reusable UI components that update efficiently and automatically when data changes. React follows a declarative approach, making it easier to manage the state of an application and render dynamic content.
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It uses VirtualDOM.
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Follows Unidirectional data flow or data binding
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Uses reusable/composable UI components to develop the view
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Increases the application’s performance with Virtual DOM
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JSX makes code easy to read and write
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It renders both on client and server side
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Easy to integrate with other frameworks (Angular, BackboneJS) since it is only a view library
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Easy to write UI Test cases and integration with tools such as JEST.
Scenario Questions
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If you need to display a list of items fetched from an API in a React component, how would you set it up?
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What happens when you update a component's state using setState? Walk me through the rendering process.
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We have a component that sometimes fails to re‑render after its props change. How would you debug the issue?
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When adding a new feature, you must choose between a class component and a functional component with hooks. What trade‑offs would you consider?
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Our app experiences performance lag when rendering a large table. How would you optimize the React rendering pipeline?
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We need to share state across many unrelated components. Which patterns would you choose and why?
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We are planning to migrate a legacy codebase from class components to functional components with hooks across multiple teams. How would you approach the migration to minimize risk?
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How would you design a component library that will be used by several product lines, ensuring consistency, versioning, and testability?
Follow-up Questions
- ❓Can you give a concrete example of a component you built?
- ❓What common pitfalls should developers watch out for when using state?
- ❓How do you decide between class components and hooks in a new feature?