Composition

React favors composition: parents pass children, slots, or render functions instead of giant prop lists. `children`, nested components, and hooks replace class inheritance for most reuse. Configuration props (`variant`, `size`) work for design systems; behavior reuse often moves into custom hooks.

Explicit composition keeps ownership visible — who provides data, who renders chrome, who handles events. It scales better than monolithic components with dozens of boolean flags.

On interviews, explain the concept with a concrete example and name the behavior interviewers probe.

Common pitfalls include hiding data flow, over-splitting components, and putting side effects in render.

The trade-off is often clarity versus reuse or explicit props versus convenience.

Checklist:

• Prefer children and small focused components.
• Extract behavior into hooks.
• Avoid prop explosion and boolean prop matrices.