Remove unnecessary useEffect and ref in usePrevious hook

docs/usePrevious.md

@@ -1,6 +1,6 @@
 # `usePrevious`
 
-React state hook that returns the previous state as described in the [React hooks FAQ](https://reactjs.org/docs/hooks-faq.html#how-to-get-the-previous-props-or-state).
+React state hook that returns the previous state as described in [Adjusting some state when a prop changes](https://react.dev/learn/you-might-not-need-an-effect#adjusting-some-state-when-a-prop-changes).
 
 ## Usage
 

src/usePrevious.ts

@@ -1,11 +1,13 @@
-import { useEffect, useRef } from 'react';
+import { useState } from 'react';
 
 export default function usePrevious<T>(state: T): T | undefined {
-  const ref = useRef<T>();
+  const [current, setCurrent] = useState<T>(state);
+  const [previous, setPrevious] = useState<T>();
 
-  useEffect(() => {
-    ref.current = state;
-  });
+  if (current !== state) {
+    setCurrent(state);
+    setPrevious(current);
+  }
 
-  return ref.current;
+  return previous;
 }