What is the 'children' prop in React and how is it used?

0-2 years experience

1. 1How would you pass a piece of JSX from a parent component to a child component using the children prop?
2. 2If you render <Card><Button/></Card>, what does the Card component receive as props?
3. 3What happens if you forget to render {props.children} inside a component that expects children?

2-5 years experience

1. 1We have a Modal component that uses React portals and also expects children. It stopped rendering its children after a recent refactor. How would you debug the issue?
2. 2When building a reusable List component, you consider using a children render prop versus an items prop with a renderItem function. What trade‑offs would you weigh?
3. 3Why might passing a large array of elements as children affect performance, and how could you mitigate it?

5-8 years experience

1. 1Our design system includes a Layout component that composes many nested children. How would you ensure type safety for children in a TypeScript codebase?
2. 2We need to support both static children and function‑as‑children patterns in a component that also forwards refs. What challenges arise and how would you implement it?
3. 3Describe how you would prevent unnecessary re‑renders of deep child trees when the parent receives new props unrelated to the children.

8+ years experience

1. 1Across several teams, you notice inconsistent usage of children vs explicit props for content injection, leading to maintenance overhead. How would you establish a unified pattern and migrate existing components?
2. 2When planning a migration from a class‑based component library to a modern hooks‑only library, what considerations around the children prop and legacy render methods should be addressed?
3. 3In a large application, you need to render a dynamic component tree based on user‑generated templates. How would you design a system that safely evaluates and renders children while avoiding XSS and performance pitfalls?