What is the difference between React and ReactDOM?
Assesses fundamental understanding of React conventions, runtime behavior, and memory/performance considerations.
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
The react package contains React.createElement(), React.Component, React.Children, and other helpers related to elements and component classes. You can think of these as the isomorphic or universal helpers that you need to build components. The react-dom package contains ReactDOM.render(), and in react-dom/server we have _server-side rendering_ support with ReactDOMServer.renderToString() and ReactDOMServer.renderToStaticMarkup().
> Modern React Note (React 18/19): ReactDOM.render was deprecated in React 18 and removed in React 19. In modern applications, always use createRoot from react-dom/client:
>
> import { createRoot } from 'react-dom/client';
> const root = createRoot(document.getElementById('root'));
> root.render(<App />);
> Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.