ReactJS Practice Test

useCallback is about keeping function references stable across renders. In React, a new function instance is created on every render, and if you pass that function down to a child component that relies on referential equality (for example a child wrapped with React.memo), the child can re-render unnecessarily just because the function prop changed. Wrapping the function with useCallback returns the same function instance unless its dependencies change, which helps prevent those extra re-renders and keeps performance where it matters. This doesn’t memoize a computed value—useMemo does that. It also isn’t about managing state or performing side effects; those are handled by useState and useEffect, respectively. So the correct idea is that useCallback memoizes stable function references to prevent unnecessary re-renders.