useRef Typed as MutableRefObject<undefined> Causes Type Error When Passed to DOM Ref Prop

useRef() with no argument infers MutableRefObject<undefined>, which is not assignable to the DOM ref prop's expected type - the fix is useRef<HTMLDivElement>(null), which produces RefObject<HTMLDivElement | null> that React's ref prop accepts

useRef must always be called with an object literal as its initial value when used with DOM elements, never null or undefined

TypeScript rejects this because ref props on native DOM elements require a callback function, not a ref object, in strict mode

The error only occurs because divRef was declared with const instead of let, preventing TypeScript from narrowing its type correctly