Конец урока

src/App.jsx

@@ -1,83 +1,67 @@
-import memo, { useMemo, useCallback, useState } from 'react'
+import React, { useState, useReducer, useRef, memo } from 'react'
 
-function MyComponent() {
+function tasksReducer(state, action) {
-    const [count, setCount] = useState(0);
+    switch(action.type) {
-    const [name, setName] = useState('John');
+        case 'ADD_TASK':
-    
+            return [...state, action.payload]
-    const greeting = useMemo(() => `Hello, ${name}!`,[name]);
+        case 'TOGGLE_TASK':
-    
+            return state.map(task => task.id === action.payload ? {...task, complite: !task.complite} : task)
+        case 'REMOVE_TASK':
+            return state.filter(task => task.id !== action.payload)
+        default:
+            return state
+    }
+}
+
+const TaskList = memo(function TaskList({tasks, onToggle, onRemove}) {
+    console.log("Rendred")
     return (
-        <>
+        <ul>
-        <h2>{greeting}</h2>
+        {tasks.map(({id, text, complite}) => (
-        <button onClick={()=>setName('Alex')}>New name</button>
+                <li key={id}
-        </>
+                    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 MyComponent2() {
-    const [data,setData] = useState([{theme:'light'}])
-    const userPreferences = useMemo(()=>({theme: 'dark', language: 'en'}),[]);
-    
-    const processData = useMemo(()=>{
-        return data.map(item => ({ ...item,theme: userPreferences.theme }))
-    },[data, userPreferences]);
-    console.log(processData);
-    return (
-        <>
-            <h2 className={data.theme}>2</h2>
-            <button onClick={()=>setData(data)}>set new theme</button>
-        </>
-    )
-}
-
-function MyComponent3() {
-    const sum = useMemo(()=> a+b,[a,b]);//Бессмысленное применение и вредное
-
-    //Применение оправдано
-    const complexResult = useMemo(()=>{
-        return heavyMethOperations(largeDataSet);
-    },[largeDataSet])
-}
-
-function ParentComponent({ items }) {
-    const [filter, setFilter] = useState('');
-    
-    const listProps = useMemo(()=>({
-            items: items.filter(item => item.name.includes(filter)),
-            onItemClick: id => console.log('Clicked',id),
-            theme: 'dark'
-        }),[items,filter]);
-    
-    return (
-        <>
-        <Memoized {...listProps} />
-        <button onClick={()=>setFilter('Bob')}>Click</button>
-        </>
-    )
-}
-
-function Memoized(props) {
-    console.log(props);
-    return (
-        <>
-        <h3 className={props.theme}>Memoized</h3>
-        {props.items.map((item) => (
-         <>
-            <li>
-                {item.name}
-            </li>
-         </>))}
-        </>
-    )
-}
 
 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}}>
-			{/* Добавьте тестовый контент для проверки */}
+			<h1>Список дел</h1>
-			<h1>Hello, React!</h1>
+			<input ref={inputRef} value={input} onChange={e => setInput(e.target.value)} />
-            <ParentComponent items={[{name:'Alex'},{name:'Bob'}]} />
+			<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>
 )