Сделали React.memo и React.useMemo

src/App.jsx

@@ -1,72 +1,50 @@
-import memo, { useMemo, useCallback, useState } from 'react'
+import { memo, useState, useMemo } from 'react'
 
-function MyComponent() {
+function memoize(fn) {
-    const [count, setCount] = useState(0);
+    const cache = new Map();
-    const [name, setName] = useState('John');
+    return function(...args) {
+        const key = JSON.stringify(args);
+        if (cache.has(key)) {
+            return cache.get(key);
+        }
+        const result = fn.apply(this, args);
+        cache.set(key,result);
+        return result;
+    }
+}
 
-    const greeting = useMemo(() => `Hello, ${name}!`,[name]);
+function fibonachi(n, memo={}) {
+    if (n in memo) {console.log(n);return memo[n];}
+    if (n <= 1) return 1;
+    memo[n] = fibonachi(n-1, memo) + fibonachi(n - 2, memo);
+    return memo[n];
+}
+
+const MyComponent = ({ value }) => {
+    console.log('Rendring');
+    return <div>{value}</div>
+}
+
+const MemoizedComponent = memo(MyComponent);
+
+const Child = memo(({ children }) => {
+    console.log('Child component rendred');
+    return <div>{children}</div>;
+});
+
+const Parent = () => {
+    const [count,setCount] = useState(0);
+    const [text, setText] = useState('');
+    
+    const stableChild = useMemo(() => <span>Memo text</span>,[]);
     
     return (
         <>
-        <h2>{greeting}</h2>
+            <Child>
-        <button onClick={()=>setName('Alex')}>New name</button>
+                {stableChild}
-        </>
+            </Child>
-    )
+            <input type="text" onChange={(e) => setText(e.target.value)} value={text} />
-}
+            <button onClick={() => setCount(count + 1)}>Increment {count}</button>
-
-function MyComponent2() {
-    const [data,setData] = useState([{theme:'light'}])
-    const userPreferences = useMemo(()=>({theme: 'dark', language: 'en'}),[]);
-    
-    const processData = useMemo(()=>{
-        return data.map(item => ({ ...item,theme: userPreferences.theme }))
-    },[data, userPreferences]);
-    console.log(processData);
-    return (
-        <>
-            <h2 className={data.theme}>2</h2>
-            <button onClick={()=>setData(data)}>set new theme</button>
-        </>
-    )
-}
-
-function MyComponent3() {
-    const sum = useMemo(()=> a+b,[a,b]);//Бессмысленное применение и вредное
-
-    //Применение оправдано
-    const complexResult = useMemo(()=>{
-        return heavyMethOperations(largeDataSet);
-    },[largeDataSet])
-}
-
-function ParentComponent({ items }) {
-    const [filter, setFilter] = useState('');
-    
-    const listProps = useMemo(()=>({
-            items: items.filter(item => item.name.includes(filter)),
-            onItemClick: id => console.log('Clicked',id),
-            theme: 'dark'
-        }),[items,filter]);
-    
-    return (
-        <>
-        <Memoized {...listProps} />
-        <button onClick={()=>setFilter('Bob')}>Click</button>
-        </>
-    )
-}
-
-function Memoized(props) {
-    console.log(props);
-    return (
-        <>
-        <h3 className={props.theme}>Memoized</h3>
-        {props.items.map((item) => (
-         <>
-            <li>
-                {item.name}
-            </li>
-         </>))}
         </>
     )
 }
@@ -74,10 +52,9 @@ function Memoized(props) {
 function App() {
 	return (
 		<>
-			{/* Добавьте тестовый контент для проверки */}
 			<h1>Hello, React!</h1>
-            <ParentComponent items={[{name:'Alex'},{name:'Bob'}]} />
+            <Parent />
-		</>
+        </>
 	)
 }