Сделали React.memo и React.useMemo

src/App.jsx

@@ -1,79 +1,60 @@
-import { useState, createContext, useContext } from 'react'
-import styles from './App.module.scss'
+import { memo, useState, useMemo } from 'react'
 
-const UserContext = createContext('')
-
-function UserProvider({ children }) {
-    const [name,setName] = useState('');
-    
-    const toggleName = (newName) => {
-        setName(newName);
+function memoize(fn) {
+    const cache = new Map();
+    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;
     }
+}
+
+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 (
-        <UserContext.Provider value={{name, toggleName}}>
-            {children}
-        </UserContext.Provider>
+        <>
+            <Child>
+                {stableChild}
+            </Child>
+            <input type="text" onChange={(e) => setText(e.target.value)} value={text} />
+            <button onClick={() => setCount(count + 1)}>Increment {count}</button>
+        </>
     )
 }
 
-function Form() {
-    const {name, toggleName} = useContext(UserContext)
-    const [newName,setNewName] = useState('');
-    const handleSubmit = (event) => {
-        event.preventDefault();
-        toggleName(event.target[0].value)
-    }
-    const handlerChange = (event) => {
-        setNewName(event.target.value);
-    }
-    return (
-        <form onSubmit={handleSubmit}>
-        <input type='text' value={newName} onChange={handlerChange} />
-        <button type='submit'>Войти</button>
-        </form>
-    )
-}
-
-function ExitButton() {
-    const {name, toggleName} = useContext(UserContext)
-    
-    return (
-        <button onClick={() => toggleName('')}>Выход</button>
-    )
-}
-
-function Toolbar() {
-    const {name, toggleName} = useContext(UserContext)
-    return(
-        <div className={styles.container}>
-            <h3>Панель пользователя</h3>
-            {name && `Привет ${name}`}
-            {name ? <ExitButton /> : <Form /> }
-            
-        </div>
-    )
-}
-
-function Page() {
-    return (
-        <div>
-            <h1 style={{textAlign: 'center'}}>Главная страница</h1>
-            <Toolbar />
-        </div>
-    )
-}
-
-function App() {    
-    
+function App() {
 	return (
 		<>
-			{/* Добавьте тестовый контент для проверки */}
 			<h1>Hello, React!</h1>
-        <UserProvider>
-            <Page />
-        </UserProvider>
-		</>
+            <Parent />
+        </>
 	)
 }
 

src/App.module.scss

@@ -1,13 +0,0 @@
-.container {
-    height: 500px;
-    border: 1px solid black;
-    border-radius: 10px;
-    background-color: lightblue;
-}
-.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>
 )