Grabbed dndbeyond's source code

```
~/go/bin/sourcemapper -output ddb -jsurl https://media.dndbeyond.com/character-app/static/js/main.90aa78c5.js
```

ddb_main/node_modules/@mui/utils/useEventCallback/useEventCallback.js

@@ -0,0 +1,20 @@
+'use client';
+
+import * as React from 'react';
+import useEnhancedEffect from '../useEnhancedEffect';
+
+/**
+ * Inspired by https://github.com/facebook/react/issues/14099#issuecomment-440013892
+ * See RFC in https://github.com/reactjs/rfcs/pull/220
+ */
+
+function useEventCallback(fn) {
+  const ref = React.useRef(fn);
+  useEnhancedEffect(() => {
+    ref.current = fn;
+  });
+  return React.useRef((...args) =>
+  // @ts-expect-error hide `this`
+  (0, ref.current)(...args)).current;
+}
+export default useEventCallback;