Сделали useReducer для счетчика

src/App.jsx

@@ -1,96 +1,50 @@
-import React from 'react'
+import { useState, useReducer } from 'react'
-import styles from './App.module.scss'
 
-class Clock extends React.Component {
+function counterReducer(state, action) {
-    constructor(props) {
+    switch (action.type) {
-        super(props);
+        case 'increment':
-        this.state = { date: new Date() };
+            return state + 1
-    }
+        case 'decrement':
-    componentDidMount() {
+            return state - 1
-        this.timerId = setInterval( () => this.tick(), 1000);
+        case 'reset':
-    }
+            return 0
-    componentWillUnmount() {
+        case 'set_value':
-        clearInterval(this.timerId)
+            return action.value
-    }
+        default:
-    tick() {
+            return state
-        this.setState({ date: new Date() })
-    }
-    render() {
-        return <div>{this.state.date.toLocaleTimeString()}</div>
     }
 }
 
-function Clock2() {
+function Counter() {
-    const [date, setDate] = React.useState(new Date());
+    const [count, dispatch] = useReducer(counterReducer,0);
     
-    React.useEffect(()=>{
+    return (
-        const timerId = setInterval(()=> setDate(new Date()),1000);
+        <div>
-        return () => clearInterval(timerId);
+            <span>Счетчик: {count}</span>
-    },[])
+            <button onClick={()=> dispatch({type: 'increment'})}>+</button>
-    
+            <button onClick={()=> dispatch({type: 'decrement'})}>-</button>
-    return <div>{date.toLocaleTimeString()}</div>
+            <button onClick={()=> dispatch({type: 'reset'})}>reset</button>
-}
+            <button onClick={()=> dispatch({type: 'set_value', value: 5})}>set 5</button>
-
-function MouseTracker() {
-    const [x,setX] = React.useState(0);
-    const [y,setY] = React.useState(0);
-    
-    const mouseMoveHandler = event => {
-        setX(event.clientX);
-        setY(event.clientY);
-    }
-    
-    React.useEffect(()=>{
-        document.addEventListener('mousemove', mouseMoveHandler);
-        return () => {
-            document.removeEventListener('mousemove',mouseMoveHandler);
-        }
-    },[]);
-    
-    return <div className={styles.container}>
-        <p>Координаты мыши:<br /> X:<b>{x}</b>, Y:<b>{y}</b></p>
         </div>
-}
+    )
-
-function DataFetcher() {
-    const [posts,setPosts] = React.useState([]);
-    const [users,setUsers] = React.useState([]);
-    
-    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 [tasks, setTasks] = useState([])
-    const [dataFetcher,setDataFetcher] = React.useState(false);
+    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>
-            <Clock />
+            <Counter />
-            <Clock2 />
-            <button onClick={() => setTracker(!tracker)}>Показать/Скрыть трекер</button>
-            { tracker && <MouseTracker /> }
-            <button onClick={() => setDataFetcher(!dataFetcher)}>Показать/Скрыть посты</button>
-            { dataFetcher && <DataFetcher /> }
 		</>
 	)
 }

src/App.module.scss

@@ -1,11 +1,15 @@
 .container {
-    width: 300px;
+/*    display: flex;
-    height: 200px;
+    flex-direction: column;
-    border: 2px dashed grey;
+    flex-wrap: nowrap;*/
-    margin: 10px;
+    height: 500px;
-    text-align: center;
+    overflow: auto;
-    p {
+    border: 1px solid black;
-        margin-top: 20%;
-    }
 }
-
+.item {
+    font-size: 16pt;
+    border: 1px dotted gray;
+    /*margin: 5px 10px;
+    padding: 10px;*/
+    border-radius: 5px;
+}