Разобрали useRef

package.json

@@ -10,7 +10,6 @@
     "preview": "vite preview"
   },
   "dependencies": {
-    "info": "^1.0.0",
     "react": "^19.1.0",
     "react-dom": "^19.1.0"
   },
@@ -23,8 +22,6 @@
     "eslint-plugin-react-hooks": "^5.2.0",
     "eslint-plugin-react-refresh": "^0.4.19",
     "globals": "^16.0.0",
-    "sass": "^1.99.0",
-    "sass-embedded": "^1.99.0",
     "vite": "^6.3.5"
   }
 }

src/App.jsx

@@ -1,29 +1,98 @@
-import styles from './styles/App.module.scss'
+import { useState, useRef, useEffect } from 'react'
-import React, { useState, useCallback } from 'react'
 
-function CounterButton({label, onClick}) {
+function Example() {
+    const myRef = useRef(null);
+    const counterRef = useRef(0);
+    const [text, setText] = useState('');
+    
+    useEffect(() => {
+        myRef.current?.focus();
+    },[]);
+        
+    const handlerFocus = () => {
+        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 countRef = useRef(0);
+    
+    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 (
-        <button onClick={onClick} className={styles.counter_button}>{label}</button>
+        <div>
+            Текущее значение: {value} <br />
+            Предыдущее значение: {prevValueRef.current}
+        </div>
     )
 }
-function CounterDisplay({value}) {
-    return (<div className={styles.counter_display}>
-            Значение счетчика: <b>{value}</b>
-    </div>)
-}
 
-function App() {
+function ScrollList() {
-    const [counter,setCounter] = useState(0);
+    const listRef = useRef(null);
     
-    const increment = () => setCounter(prev => prev + 1);
+    const scrollToBottom = () => {
-    const decrement = () => setCounter(prev => prev - 1);
+        if(listRef.current) {
+            listRef.current.scrollTop = listRef.current.scrollHeight;
+        }
+    }
         
     return (
         <>
-            <h2>Практика по созданию счетчика с колбэками</h2>
+            <div ref={listRef} 
-            <CounterButton label="Увеличить" onClick={increment} />
+               style={{height: 200, overflowY: 'auto', border: '1px solid black'}}>
-            <CounterButton label="уменьшить" onClick={decrement} />
+                {[...Array(20)].map((_,i)=>(
-            <CounterDisplay value={counter} />
+                    <div key={i}>Элемент № {i + 1}</div>
+                ))}
+            </div>
+            <button onClick={scrollToBottom}>Прокрутить вниз</button>
+        </>
+    )
+}
+        
+function App() {
+    
+    
+	return (
+		<>
+			<h1>Hello, React!</h1>
+            <ScrollList />
 		</>
 	)
 }

src/main.jsx

@@ -1,10 +1,8 @@
 import { StrictMode } from 'react'
 import { createRoot } from 'react-dom/client'
-
+// удаляем import './index.css'
 import App from './App.jsx'
 
 createRoot(document.getElementById('root')).render(
-	<StrictMode>
 		<App />
-	</StrictMode>
 )

src/styles/App.module.scss

@@ -1,22 +0,0 @@
-.container {
-    display:flex;
-    flex-direction: row;
-    border: 1px solid black;
-    border-radius: 5px;
-    margin-bottom: 10px;
-    p {
-        padding: 5px 10px;
-    }
-}
-.counter {
-    &_display{
-        border: 1px solid black;
-        border-width: 3px;
-        border-radius: 10px;
-        padding: 10px;
-        width: 300px;
-    }
-    &_button{
-        padding: 10px;
-    }
-}