Vanilla JavaScript excels for small interactions: one form, one toggle, one fetch. React earns its keep when UI state, nesting, and reuse grow—dashboards, wizards, design systems.
When vanilla is enough
- Marketing pages with minimal interactivity
- Progressive enhancement on server-rendered HTML
- Embedded widgets where bundle size must stay tiny
When React helps
- Many components sharing and updating the same state
- Complex forms with validation and dependent fields
- Teams needing consistent patterns, testing, and typed props
- Products that may share logic with React Native mobile apps
Trade-offs
React adds a runtime, build step (in real apps), and learning curve. You gain structure, ecosystem, and hiring relevance. Neither approach is “wrong”—match the tool to scope and team.
Important interview questions and answers
- Q: Should every site use React?
A: No. Static content and light interactivity often need no framework. - Q: What is the main cost of React?
A: Bundle size, abstraction overhead, and the need to learn component patterns and hooks. - Q: Can you mix React and vanilla?
A: Yes—mount React on a root node inside otherwise static HTML, or use refs for non-React widgets.
Self-check
- Give one scenario where you would stay vanilla.
- Give one scenario where components and hooks pay off.