Сделали таймер

src/App.jsx

@@ -1,45 +1,108 @@
-import React, { useMemo, useCallback, useState } from 'react'
+import React from 'react'
 
-const TodoItem = React.memo(({ item, onToggle, onDelete }) => {
+class MyComponent extends React.Component {
-    console.log(`rendred ${item.id}`);
+    constructor(props) {
-    return <li>
+        super(props);
-            {item.name}
+        this.state = { data: null };
-            <button onClick={() => onToggle(item.id)}>Done</button>
+        this.handleClick = this.handleClick.bind(this);
-            <button onClick={() => onDelete(item.id)}>remove</button>
+    }
-        </li>
-})
     
-function ItemList({ items }) {
+    render() {
+        return (
+            <div>
+            {this.state.data ? (
+                    <div>Данные: {this.state.data}</div>
+                ) : (
+                    <div>Загрузка...</div>
+                )}
+                <button onClick={this.handleClick}>Обновить</button>
+            </div>
+        )
+    }
     
-    const handleToggle = useCallback(id => {
+    componentDidMount() {
-        items.done = true;
+        fetch('https://api.example.com/data')
-        console.log(`Item ${id} done`)
+        .then(responce => responce.json())
-        console.log(id)
+        .then(json => this.setState({data: json}));
-    },[]);
         
-    const handleDelete = useCallback(id => {
+        this.timerId = setInterval(()=> console.log('Tick'), 1000);
-        items.pop(id);
+    }
-    },[]);
+    
-    return (
+    componentWillUnmout() {
-        <>
+        clearInterval(this.timerId);
-            <h3>List items</h3>
+    }
-            {items.map(item => (
+    
-             <TodoItem key={item.id} item={item}
+    handleClick() {
-              onToggle={handleToggle} onDelete={handleDelete} />
+        this.setState({data: 'Данные'})
-             ))}
+    }
-        </>
+}
-    )
+
+class MyComponent2 extends React.Component {
+    controller = new AbortController()
+
+    componentDidMount() {
+        fetch('https://api.example.com/data',{ singnal: this.controller.signal })
+        .then(responce => responce.json())
+        .then(json => this.setState({data: json}))
+        .catch(error => {
+            if(error.name == 'AbortError') {
+                console.log('Aborted');
+            } else {
+                console.log('Other error',error);
+            }
+        });
+    }
+
+    componentWillUnmount() {
+        this.controller.abort()
+    }
+}
+class MyComponent3 extends React.Component {
+    componentDidMount() {
+        this.loadData();
+    }
+    
+    async loadData() {
+        try {
+            const response = await fetch('https://api.example.com/data');
+            const data = await response.json();
+            this.setSate({ data });
+        } catch {
+            console.log('error');
+        }
+    }
+}
+
+class Timer extends React.Component {
+    constructor(props) {
+        super(props);
+        this.state = { seconds: 0 }
+    }
+    
+    componentDidMount() {
+        console.log('Timer mounted');
+        this.interval = setInterval(()=>{
+            this.setState(prevState => ({seconds: prevState.seconds + 1}))
+        },1000);
+    }
+    
+    componentWillUnmount() {
+        console.log('Timer unmount');
+        clearInterval(this.interval);
+    }
+    render() {
+        return <h2>Прошло секунд: {this.state.seconds}</h2>
+    }
 }
 
 function App() {
+    const [show,setShow] = React.useState(true);
+    
 	return (
 		<>
-			{/* Добавьте тестовый контент для проверки */}
+			<h1>Таймер с классом</h1>
-			<h1>Hello, React!</h1>
+            <button onClick={()=>setShow(prev => !prev)}>{show ? 'Скрыть' : 'Показать'} таймер</button>
-            <ItemList items={[
+            {show && <Timer />}
-                {id:1,name:'Первый',done:false},
-                {id:2,name:'Второй',done:false}
-            ]} />
 		</>
 	)
 }