useMutationObserver

Watch for changes being made to the DOM tree. MutationObserver MDN

useMutationObserver wraps the native MutationObserver API to watch for changes in the DOM subtree of a target element. It fires a callback with the list of MutationRecord entries whenever observed mutations occur. The hook returns a stop function to disconnect the observer at any time.

When to Use

• Reacting to attribute changes on elements controlled by third-party libraries
• Monitoring dynamic DOM changes such as child node additions or removals in content-editable areas
• Building devtools or debugging utilities that track DOM mutations in real time

Notes

• Configuration: Pass standard MutationObserverInit options (attributes, childList, subtree, characterData, etc.) to control which types of mutations are observed.
• Cleanup: The observer is automatically disconnected on unmount. Use the returned stop function for early disconnection.
• See also useResizeObserver for observing size changes and useIntersectionObserver for visibility changes.

Usage

function Demo() {
  const options = { attributes: true };
  const [width, setWidth] = useState(200);
  const [count, setCount] = useState(0);

  const ref = useRef<HTMLDivElement>(null);

  const stop = useMutationObserver(
    (mutationsList) => {
      mutationsList.forEach(() => setCount(c => c + 1));
    },
    ref,
    options,
  );

  useEffect(() => {
    setWidth(300);
  }, []);

  return (
    <div>
      <div
        ref={ref}
        style={{
          width,
          padding: 12,
          border: "1px solid #000",
          marginBottom: 8,
        }}
      >
        current width：{width}
      </div>
      <button onClick={() => setWidth(w => w + 10)}>widening</button>
      <button onClick={() => stop()}>stop observe</button>
      <p>Mutation count {count}</p>
    </div>
  );
};

API

UseMutationObserver

Returns

() => void: stop listenering function

Arguments

BasicTarget

export type BasicTarget<T extends TargetType = Element> = (() => TargetValue<T>) | TargetValue<T> | MutableRefObject<TargetValue<T>>;

TargetValue

type TargetValue<T> = T | undefined | null;

TargetType

type TargetType = HTMLElement | Element | Window | Document | EventTarget;