Конец урока

src/App.jsx

@@ -1,99 +1,67 @@
-import { useState, useRef, useEffect } from 'react'
+import React, { useState, useReducer, useRef, memo } from 'react'
 
-function Example() {
+function tasksReducer(state, action) {
-    const myRef = useRef(null);
+    switch(action.type) {
-    const counterRef = useRef(0);
+        case 'ADD_TASK':
-    const [text, setText] = useState('');
+            return [...state, action.payload]
-    
+        case 'TOGGLE_TASK':
-    useEffect(() => {
+            return state.map(task => task.id === action.payload ? {...task, complite: !task.complite} : task)
-        myRef.current?.focus();
+        case 'REMOVE_TASK':
-    },[]);
+            return state.filter(task => task.id !== action.payload)
-        
+        default:
-    const handlerFocus = () => {
+            return state
-        if(myRef.current) {
-            myRef.current.focus();
-        }
-    };
-    
-    const handlerChange = (event) => {
-        setText(event.target.value);
     }
-    counterRef.current += 1;
-    return <div>
-        <input ref={myRef} text="text" /><br />
-        Количество рендров: {counterRef.current}<br />
-        <input text="text" onChange={handlerChange} value={text} />
-        <button onClick={handlerFocus}>Поставить фокус на поле</button>
-    </div>
 }
 
-function ClickCounter() {
+const TaskList = memo(function TaskList({tasks, onToggle, onRemove}) {
-    const countRef = useRef(0);
+    console.log("Rendred")
-    
-    function handlerClick() {
-        countRef.current += 1;
-        //alert(`Нажали ${countRef.current} раз.`);
-    }
-    return <button onClick={handlerClick}>Нажать</button>;
-}
-
-function TimerComponent() {
-    const timerIdRef = useRef(null);
-    
-    useEffect(() => {
-        timerIdRef.current = setTimeout(() => {
-            alert("Прошло 3 секунды");
-        }, 3000);
-        return () => {
-            clearTimeout(timerIdRef.current);
-        }
-    },[]);
-}
-
-function PrevValue({ value }) {
-    const prevValueRef = useRef();
-    
-    useEffect(() => {
-        prevValueRef.current = value;
-    });
     return (
-        <div>
+        <ul>
-            Текущее значение: {value} <br />
+        {tasks.map(({id, text, complite}) => (
-            Предыдущее значение: {prevValueRef.current}
+                <li key={id}
-        </div>
+                    style={{textDecoration: complite ? 'line-through' : 'none' }}>
+                    <input type="checkbox" checked={complite} onChange={()=>onToggle(id)} />
+                    {text}
+                    <button onClick={()=> onRemove(id)} style={{marginLeft: 10}}>
+                        Удалить
+                    </button>
+                </li>
+            ))}
+        </ul>
     )
-}
+})
 
-function ScrollList() {
-    const listRef = useRef(null);
-    
-    const scrollToBottom = () => {
-        if(listRef.current) {
-            listRef.current.scrollTop = listRef.current.scrollHeight;
-        }
-    }
-        
-    return (
-        <>
-            <div ref={listRef} 
-               style={{height: 200, overflowY: 'auto', border: '1px solid black'}}>
-                {[...Array(20)].map((_,i)=>(
-                    <div key={i}>Элемент № {i + 1}</div>
-                ))}
-            </div>
-            <button onClick={scrollToBottom}>Прокрутить вниз</button>
-        </>
-    )
-}
-        
 function App() {
+    const [tasks, dispatch] = useReducer(tasksReducer,[])
+    const [input,setInput] = useState('')
+    const [error,setError] = useState('')
+    const inputRef = useRef(null)
     
+    const addTask = () => {
+        if (input.trim() === '') {
+            setError('Пустой текст задачи')
+            return
+        }
+        setError('')
+        dispatch({
+            type: 'ADD_TASK',
+            payload: {id: Date.now(), text: input.trim(), complite: false }
+        })
+        setInput('')
+        inputRef.current.focus()
+    }
     
 	return (
-		<>
+		<div style={{padding: 20}}>
-			<h1>Hello, React!</h1>
+			<h1>Список дел</h1>
-            <ScrollList />
+			<input ref={inputRef} value={input} onChange={e => setInput(e.target.value)} />
-		</>
+			<button onClick={addTask}>Добавить</button>
+            {error && <p style={{color: 'red'}}>{error}</p>}
+            
+            <TaskList tasks={tasks} 
+                onToggle={id => dispatch({type: 'TOGGLE_TASK', payload: id})}
+                onRemove={id => dispatch({type: 'REMOVE_TASK', payload: id})} />
+		</div>
 	)
 }
 

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>
 )