React interview questions

Write mergeDefaultProps(props, defaults). It returns a new plain object that has every key from defaults, overridden by any key present in props whose value is not undefined. Neither input object should be mutated. This is the logic behind default props: a caller who does not

Write buildClassName(base, conditional). base is a string (possibly with several space-separated classes). conditional is an object mapping class name to a boolean. Return a single space-separated class string containing base's classes followed by every key of conditional whose

In plain terms: what is a React component, and what are props? Give me a concrete example of a parent handing something to a child.

You write <Card title="Hi">text</Card> in a .jsx file. What does that line actually turn into when the code runs, and why does a component have to return a single root node?

Write composeProviderValues(values). values is an array of plain objects, representing a stack of nested Context.Provider values from outermost to innermost. Merge them into the single object a component deep in the tree would end up seeing if each provider spread the outer

In plain terms: what is "prop drilling", and how does React Context give you a way around it?