Сделали компонент часов

src/App.jsx

@@ -1,59 +1,44 @@
-import { memo, useState, useMemo } from 'react'
+import React from 'react'
 
-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;
-    }
+class Clock extends React.Component {
+    constructor(props) {
+        super(props)
+        this.state = { time: new Date().toLocaleTimeString() }
     }
     
-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];
+    componentDidMount() {
+        this.timerId = setInterval(()=>{
+            this.setState({ time: new Date().toLocaleTimeString() })
+        }, 1000);
+        console.log('Таймер смонтирован')
     }
     
-const MyComponent = ({ value }) => {
-    console.log('Rendring');
-    return <div>{value}</div>
+    componentDidUpdate(prevProps,prevState) {
+        console.log('Компонент обнвлен')
     }
     
-const MemoizedComponent = memo(MyComponent);
+    componentWillUnmount() {
+        clearInterval(this.timerId)
+        console.log('Компонент таймера размонтирован')
+    }
     
-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 (
-        <>
-            <Child>
-                {stableChild}
-            </Child>
-            <input type="text" onChange={(e) => setText(e.target.value)} value={text} />
-            <button onClick={() => setCount(count + 1)}>Increment {count}</button>
-        </>
-    )
+    render() {
+        return <div>
+            <h2>Текущее время: {this.state.time}</h2>
+            </div>
+    }
 }
 
 function App() {
+    const [showClock, setShowClock] = React.useState(true);
+    
 	return (
 		<>
-			<h1>Hello, React!</h1>
-            <Parent />
+			<h1>Жизненный цикл компонента часов</h1>
+            <button onClick={()=> setShowClock(!showClock)}>
+                {showClock ? 'Скрыть часы' : 'Показать часы' }
+            </button>
+            {showClock && <Clock />}
 		</>
 	)
 }