Что то доделали. Надо сменить ветку

src/App.jsx

@@ -1,45 +1,96 @@
-import React, { useMemo, useCallback, useState } from 'react'
+import React from 'react'
+import styles from './App.module.scss'
 
-const TodoItem = React.memo(({ item, onToggle, onDelete }) => {
+class Clock extends React.Component {
-    console.log(`rendred ${item.id}`);
+    constructor(props) {
-    return <li>
+        super(props);
-            {item.name}
+        this.state = { date: new Date() };
-            <button onClick={() => onToggle(item.id)}>Done</button>
+    }
-            <button onClick={() => onDelete(item.id)}>remove</button>
+    componentDidMount() {
-        </li>
+        this.timerId = setInterval( () => this.tick(), 1000);
-})
+    }
+    componentWillUnmount() {
+        clearInterval(this.timerId)
+    }
+    tick() {
+        this.setState({ date: new Date() })
+    }
+    render() {
+        return <div>{this.state.date.toLocaleTimeString()}</div>
+    }
+}
 
-function ItemList({ items }) {
+function Clock2() {
+    const [date, setDate] = React.useState(new Date());
+    
+    React.useEffect(()=>{
+        const timerId = setInterval(()=> setDate(new Date()),1000);
+        return () => clearInterval(timerId);
+    },[])
+    
+    return <div>{date.toLocaleTimeString()}</div>
+}
 
-    const handleToggle = useCallback(id => {
+function MouseTracker() {
-        items.done = true;
+    const [x,setX] = React.useState(0);
-        console.log(`Item ${id} done`)
+    const [y,setY] = React.useState(0);
-        console.log(id)
+    
+    const mouseMoveHandler = event => {
+        setX(event.clientX);
+        setY(event.clientY);
+    }
+    
+    React.useEffect(()=>{
+        document.addEventListener('mousemove', mouseMoveHandler);
+        return () => {
+            document.removeEventListener('mousemove',mouseMoveHandler);
+        }
     },[]);
     
-    const handleDelete = useCallback(id => {
+    return <div className={styles.container}>
-        items.pop(id);
+        <p>Координаты мыши:<br /> X:<b>{x}</b>, Y:<b>{y}</b></p>
-    },[]);
+        </div>
-    return (
+}
-        <>
+
-            <h3>List items</h3>
+function DataFetcher() {
-            {items.map(item => (
+    const [posts,setPosts] = React.useState([]);
-             <TodoItem key={item.id} item={item}
+    const [users,setUsers] = React.useState([]);
-              onToggle={handleToggle} onDelete={handleDelete} />
+    
-             ))}
+    const getPosts = async () => {
-        </>
+        const response = await fetch('https://jsonplaceholder.typicode.com/posts');
-    )
+        const data = await response.json();
+        setUsers(data.reduce((acc, value) => {
+            if (!(value.userId in acc))
+                return [...acc,value.userId]
+            return acc
+        }))
+        console.log(users);
+        setPosts(data.slice(1,10));
+        
+    }
+    
+    React.useEffect(() => {
+        console.log("Компонент создан");
+        getPosts();
+        return () => {console.log("Компонент удален");setPosts([])};
+    },[])
+    
+    return <div><ol>{posts.map(post => <li id={post.id}>{post.title}</li>)}</ol></div>
 }
 
 function App() {
+    const [tracker,setTracker] = React.useState(false);
+    const [dataFetcher,setDataFetcher] = React.useState(false);
+    
 	return (
 		<>
-			{/* Добавьте тестовый контент для проверки */}
 			<h1>Hello, React!</h1>
-            <ItemList items={[
+            <Clock />
-                {id:1,name:'Первый',done:false},
+            <Clock2 />
-                {id:2,name:'Второй',done:false}
+            <button onClick={() => setTracker(!tracker)}>Показать/Скрыть трекер</button>
-            ]} />
+            { tracker && <MouseTracker /> }
+            <button onClick={() => setDataFetcher(!dataFetcher)}>Показать/Скрыть посты</button>
+            { dataFetcher && <DataFetcher /> }
 		</>
 	)
 }

src/App.module.scss

@@ -0,0 +1,11 @@
+.container {
+    width: 300px;
+    height: 200px;
+    border: 2px dashed grey;
+    margin: 10px;
+    text-align: center;
+    p {
+        margin-top: 20%;
+    }
+}
+

src/main.jsx

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