useImperativeHandle-example.ts

function FancyInput(props, ref) {
  const inputRef = useRef();
  useImperativeHandle(ref, () => ({
    focus: () => {
      inputRef.current.focus();
    }
  }));
  return <input ref={inputRef} ... />;
}
FancyInput = React.forwardRef(FancyInput);

// You can now get a ref directly to the DOM button:
const fancyInputRef = React.createRef();
<FancyInput ref={fancyInputRef}>Click me!</FancyInput>;

function FancyInput(props, ref) {
It is not typescript code. Props and ref should not tot be any.

Use should use

const FancyInput: ForwardRefRenderFunction<HTMLInputElement, FancyInputProps>

And you will get type error

useImperativeHandle(ref, () => ({
    focus: () => {
      inputRef.current.focus();
    }
  }));