type MutableRefObject<T> = {
    current: T | null;  // generic type 
};



  const abortController: MutableRefObject<AbortController> = useRef(null);
    
  const doRequest = () => {
          abortController.current = new AbortController();
          window
              .fetch(url, {
                  method: 'GET',
                  signal: abortController.current.signal,
              })
              .then(res => res.json());
      };

      

const cancelRequest = () => {
        abortController.current?.abort();  // ? for Optional chaining
};

Basically the type of AbortController is AbortController . I created the type MutableRefObject for useRef hook . The RefObject provided by React throws another error because the current property is readonly on RefObject .

It's because you are missing the value DOM in the lib array of your tsconfig.json. If you check the official repo, you will find the AbortController here!