Сделали React.memo и React.useMemo

src/App.jsx

@@ -1,51 +1,60 @@
-import { useState, useReducer } from 'react'
+import { memo, useState, useMemo } from 'react'
 
-function counterReducer(state, action) {
+function memoize(fn) {
-    switch (action.type) {
+    const cache = new Map();
-        case 'increment':
+    return function(...args) {
-            return state + 1
+        const key = JSON.stringify(args);
-        case 'decrement':
+        if (cache.has(key)) {
-            return state - 1
+            return cache.get(key);
-        case 'reset':
+        }
-            return 0
+        const result = fn.apply(this, args);
-        case 'set_value':
+        cache.set(key,result);
-            return action.value
+        return result;
-        default:
-            return state
     }
 }
 
-function Counter() {
+function fibonachi(n, memo={}) {
-    const [count, dispatch] = useReducer(counterReducer,0);
+    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 (
-        <div>
+        <>
-            <span>Счетчик: {count}</span>
+            <Child>
-            <button onClick={()=> dispatch({type: 'increment'})}>+</button>
+                {stableChild}
-            <button onClick={()=> dispatch({type: 'decrement'})}>-</button>
+            </Child>
-            <button onClick={()=> dispatch({type: 'reset'})}>reset</button>
+            <input type="text" onChange={(e) => setText(e.target.value)} value={text} />
-            <button onClick={()=> dispatch({type: 'set_value', value: 5})}>set 5</button>
+            <button onClick={() => setCount(count + 1)}>Increment {count}</button>
-        </div>
+        </>
     )
 }
 
 function App() {
-    const [tasks, setTasks] = useState([])
-    const [filter, setFilter] = useState('all')
-    const [sortBy,setSortBy] = useState('date')
-    
-    const addTask = newTask => {
-        setTasks([...tasks,newTask])
-    }
-    
-    
-    
 	return (
 		<>
-			{/* Добавьте тестовый контент для проверки */}
 			<h1>Hello, React!</h1>
-            <Counter />
+            <Parent />
-		</>
+        </>
 	)
 }
 

src/App.module.scss

@@ -1,15 +0,0 @@
-.container {
-/*    display: flex;
-    flex-direction: column;
-    flex-wrap: nowrap;*/
-    height: 500px;
-    overflow: auto;
-    border: 1px solid black;
-}
-.item {
-    font-size: 16pt;
-    border: 1px dotted gray;
-    /*margin: 5px 10px;
-    padding: 10px;*/
-    border-radius: 5px;
-}

src/main.jsx

@@ -4,7 +4,5 @@ import { createRoot } from 'react-dom/client'
 import App from './App.jsx'
 
 createRoot(document.getElementById('root')).render(
-	<StrictMode>
 		<App />
-	</StrictMode>
 )