Разобрали useRef

package-lock.json

@@ -8,7 +8,6 @@
       "name": "store-client",
       "version": "0.0.0",
       "dependencies": {
-        "@tanstack/react-query": "^5.100.14",
         "react": "^19.1.0",
         "react-dom": "^19.1.0"
       },
@@ -1305,32 +1304,6 @@
         "win32"
       ]
     },
-    "node_modules/@tanstack/query-core": {
-      "version": "5.100.14",
-      "resolved": "https://registry.npmjs.org/@tanstack/query-core/-/query-core-5.100.14.tgz",
-      "integrity": "sha512-5X41dGpxgeaHISCRW2oYwcSycZeULZzAunaudXT9ov1KOTj9xwt0CH6hbwqP1/z74ZWF7rYFnDpyYH07XFcZew==",
-      "license": "MIT",
-      "funding": {
-        "type": "github",
-        "url": "https://github.com/sponsors/tannerlinsley"
-      }
-    },
-    "node_modules/@tanstack/react-query": {
-      "version": "5.100.14",
-      "resolved": "https://registry.npmjs.org/@tanstack/react-query/-/react-query-5.100.14.tgz",
-      "integrity": "sha512-oOr6aRdSFEwWhzxEkD/9ZcItM3+LjBSkeVmadWKwUssAHTsqd/7bOjWrX4AbvEkoEhgAxzN0Xk6H/aYzXiYBAw==",
-      "license": "MIT",
-      "dependencies": {
-        "@tanstack/query-core": "5.100.14"
-      },
-      "funding": {
-        "type": "github",
-        "url": "https://github.com/sponsors/tannerlinsley"
-      },
-      "peerDependencies": {
-        "react": "^18 || ^19"
-      }
-    },
     "node_modules/@types/babel__core": {
       "version": "7.20.5",
       "resolved": "https://registry.npmjs.org/@types/babel__core/-/babel__core-7.20.5.tgz",

package.json

@@ -4,13 +4,12 @@
   "version": "0.0.0",
   "type": "module",
   "scripts": {
-    "dev": "vite",
+    "dev": "vite", 
     "build": "vite build",
     "lint": "eslint .",
     "preview": "vite preview"
   },
   "dependencies": {
-    "@tanstack/react-query": "^5.100.14",
     "react": "^19.1.0",
     "react-dom": "^19.1.0"
   },

src/App.jsx

@@ -1,93 +1,98 @@
-import React, {useState, useEffect, useRef } from 'react'
-//import { useQuery } from '@tanstack/react-query'
+import { useState, useRef, useEffect } from 'react'
 
-function useWindowWidth() {
-    const [width,setWidth] = useState(window.innerWidth)
+function Example() {
+    const myRef = useRef(null);
+    const counterRef = useRef(0);
+    const [text, setText] = useState('');
     
     useEffect(() => {
-        const handleResize = () => setWidth(window.innerWidth);
-        window.addEventListener('resize',handleResize);
-        return () => window.removeEventListener('resize',handleResize);
-    },[])
+        myRef.current?.focus();
+    },[]);
+        
+    const handlerFocus = () => {
+        if(myRef.current) {
+            myRef.current.focus();
+        }
+    };
     
-    return width
+    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 useLocalStorage(key, initValue) {
-    const [value, setValue] = useState(()=>{
-        const stored = localStorage.getItem(key);
-        return stored !== null ? JSON.parse(stored) : initValue
-    })
+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(() => {
-        localStorage.setItem(key, JSON.stringify(value))
-    },[key, value])
-    
-    return [value,setValue]
+        timerIdRef.current = setTimeout(() => {
+            alert("Прошло 3 секунды");
+        }, 3000);
+        return () => {
+            clearTimeout(timerIdRef.current);
+        }
+    },[]);
 }
-/*
-function useUserData(userId) {
-    return useQuery(
-        ['user',userId],
-        () => fetch(`/api/user/${userId}`).then(res => res.json()),
-        {refetchOnWindowFocus: false}
+
+function PrevValue({ value }) {
+    const prevValueRef = useRef();
+    
+    useEffect(() => {
+        prevValueRef.current = value;
+    });
+    return (
+        <div>
+            Текущее значение: {value} <br />
+            Предыдущее значение: {prevValueRef.current}
+        </div>
     )
-}*/
+}
 
-function useInput(initValue, validate) {
-    const [value, setValue] = useState(initValue);
-    const [error, setError] = useState(null);
+function ScrollList() {
+    const listRef = useRef(null);
     
-    const onChange = e => {
-        const newValue = e.target.value
-        setValue(newValue)
-        if (validate) {
-            const validationResult = validate(newValue)
-            setError(validationResult)
+    const scrollToBottom = () => {
+        if(listRef.current) {
+            listRef.current.scrollTop = listRef.current.scrollHeight;
         }
     }
-    
-    return { value, error, onChange }
-}
-
-function useInterval(callback, delay) {
-    const savedCallback = useRef()
-    
-    useEffect(()=>{
-        savedCallback.current = callback
-    },[callback]);
-    
-    useEffect(()=>{
-        if (delay == null) return
-        const id = setInterval(()=>{
-            savedCallback.current()
-        },delay);
-        return () => clearInterval(id);
-    },[delay])
-}
-
-function App() {
-    const width = useWindowWidth();
-    const [theme, setTheme] = useLocalStorage('theme','light');
-    
-    const username = useInput(
-        '',
-        value => value.length < 3 ? 'минимум 3 символа' : null
+        
+    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() {
+    
     
 	return (
 		<>
-			<h1>Hello, React!{width}</h1>
-            <button onClick={()=>{
-                setTheme(theme === 'light' ? 'dark' : 'light')
-            }}>
-                Сменить тему
-            </button>
-            <p><input type="text" 
-                value={username.value} 
-                onChange={username.onChange} />
-                { username.error ? username.error : '' }
-            </p>
+			<h1>Hello, React!</h1>
+            <ScrollList />
 		</>
 	)
 }

src/main.jsx

@@ -4,7 +4,5 @@ import { createRoot } from 'react-dom/client'
 import App from './App.jsx'
 
 createRoot(document.getElementById('root')).render(
-	<StrictMode>
 		<App />
-	</StrictMode>
 )