useMemo

package-lock.json

@@ -9,8 +9,7 @@
       "version": "0.0.0",
       "dependencies": {
         "react": "^19.1.0",
-        "react-dom": "^19.1.0",
-        "react-intl": "^10.1.13"
+        "react-dom": "^19.1.0"
       },
       "devDependencies": {
         "@eslint/js": "^9.25.0",
@@ -899,38 +898,6 @@
         "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
       }
     },
-    "node_modules/@formatjs/fast-memoize": {
-      "version": "3.1.6",
-      "resolved": "https://registry.npmjs.org/@formatjs/fast-memoize/-/fast-memoize-3.1.6.tgz",
-      "integrity": "sha512-H5aexk1Le7T9TPmscacZ+1pR6CTa2n1wq+HDVGXhH8TzUlQQpeXzZs91dRtmFHrbeNbjPFPfQujUqm7MHgVoXQ==",
-      "license": "MIT"
-    },
-    "node_modules/@formatjs/icu-messageformat-parser": {
-      "version": "3.5.11",
-      "resolved": "https://registry.npmjs.org/@formatjs/icu-messageformat-parser/-/icu-messageformat-parser-3.5.11.tgz",
-      "integrity": "sha512-NVsuNsc2dUVG9+4HBJ/srScxtA/18LqGgwtop/tuN/OIBjVl6QA+0KhfZQddDD9sEh2LeVjLFPGVU3ixa3blcA==",
-      "license": "MIT",
-      "dependencies": {
-        "@formatjs/icu-skeleton-parser": "2.1.10"
-      }
-    },
-    "node_modules/@formatjs/icu-skeleton-parser": {
-      "version": "2.1.10",
-      "resolved": "https://registry.npmjs.org/@formatjs/icu-skeleton-parser/-/icu-skeleton-parser-2.1.10.tgz",
-      "integrity": "sha512-XuSva+8ZGawk8VnD5VD6UeH8KarQ/Z022zgjHDoHmlNiAewstXuuzXc0Hk5pGFSdG+nNw5bfJKXqj1ZXHn9yUA==",
-      "license": "MIT"
-    },
-    "node_modules/@formatjs/intl": {
-      "version": "4.1.13",
-      "resolved": "https://registry.npmjs.org/@formatjs/intl/-/intl-4.1.13.tgz",
-      "integrity": "sha512-dufOl09iREq8V+laVdlGuyoqNmuzqDvyeA3O3k+0XQfvKJgK8bBWFKqYYWejFMKeOij/4LuPKJA+LsshpXQ4sw==",
-      "license": "MIT",
-      "dependencies": {
-        "@formatjs/fast-memoize": "3.1.6",
-        "@formatjs/icu-messageformat-parser": "3.5.11",
-        "intl-messageformat": "11.2.8"
-      }
-    },
     "node_modules/@humanfs/core": {
       "version": "0.19.1",
       "resolved": "https://registry.npmjs.org/@humanfs/core/-/core-0.19.1.tgz",
@@ -1400,6 +1367,7 @@
       "version": "19.1.6",
       "resolved": "https://registry.npmjs.org/@types/react/-/react-19.1.6.tgz",
       "integrity": "sha512-JeG0rEWak0N6Itr6QUx+X60uQmN+5t3j9r/OVDtWzFXKaj6kD1BwJzOksD0FF6iWxZlbE1kB0q9vtnU2ekqa1Q==",
+      "dev": true,
       "license": "MIT",
       "dependencies": {
         "csstype": "^3.0.2"
@@ -1651,6 +1619,7 @@
       "version": "3.1.3",
       "resolved": "https://registry.npmjs.org/csstype/-/csstype-3.1.3.tgz",
       "integrity": "sha512-M1uQkMl8rQK/szD0LNhtqxIPLpimGm8sOBwU7lLnCpSbTyY3yeU1Vc7l4KT5zT4s/yOxHH5O7tIuuLOCnLADRw==",
+      "dev": true,
       "license": "MIT"
     },
     "node_modules/debug": {
@@ -2112,16 +2081,6 @@
         "node": ">=0.8.19"
       }
     },
-    "node_modules/intl-messageformat": {
-      "version": "11.2.8",
-      "resolved": "https://registry.npmjs.org/intl-messageformat/-/intl-messageformat-11.2.8.tgz",
-      "integrity": "sha512-l323RCl3qJDVQ8U9j74ut/hVMdg3VPsOHpVMDvFfz9qiq4dPO5ooVYFNVUzzrpgG39a+RLzcXyJb8VFgIU+tUA==",
-      "license": "BSD-3-Clause",
-      "dependencies": {
-        "@formatjs/fast-memoize": "3.1.6",
-        "@formatjs/icu-messageformat-parser": "3.5.11"
-      }
-    },
     "node_modules/is-extglob": {
       "version": "2.1.1",
       "resolved": "https://registry.npmjs.org/is-extglob/-/is-extglob-2.1.1.tgz",
@@ -2502,21 +2461,6 @@
         "react": "^19.1.0"
       }
     },
-    "node_modules/react-intl": {
-      "version": "10.1.13",
-      "resolved": "https://registry.npmjs.org/react-intl/-/react-intl-10.1.13.tgz",
-      "integrity": "sha512-3aKnIOIPN6CWsu3jqPpYMlJZ2U0Qnxhd42xGWQNdGIknK/gBudWOHSIx9vN4XKkITokJLr7YTgs4yLUGtbvP9g==",
-      "license": "BSD-3-Clause",
-      "dependencies": {
-        "@formatjs/icu-messageformat-parser": "3.5.11",
-        "@formatjs/intl": "4.1.13",
-        "intl-messageformat": "11.2.8"
-      },
-      "peerDependencies": {
-        "@types/react": "19",
-        "react": "19"
-      }
-    },
     "node_modules/react-refresh": {
       "version": "0.17.0",
       "resolved": "https://registry.npmjs.org/react-refresh/-/react-refresh-0.17.0.tgz",

package.json

@@ -4,15 +4,14 @@
   "version": "0.0.0",
   "type": "module",
   "scripts": {
-    "dev": "vite",
+    "dev": "vite", 
     "build": "vite build",
     "lint": "eslint .",
     "preview": "vite preview"
   },
   "dependencies": {
     "react": "^19.1.0",
-    "react-dom": "^19.1.0",
-    "react-intl": "^10.1.13"
+    "react-dom": "^19.1.0"
   },
   "devDependencies": {
     "@eslint/js": "^9.25.0",

src/App.jsx

@@ -1,30 +1,82 @@
-import { IntlProvider,
-        FormattedMessage,
-        FormattedNumber,
-        FormattedDate,
-        FormattedTime,
-        FormattedDateTimeRange } from 'react-intl'
-import messageRu from './translations/ru.json'
-import messageEn from './translations/en.json'
+import memo, { useMemo, useCallback, useState } from 'react'
+
+function MyComponent() {
+    const [count, setCount] = useState(0);
+    const [name, setName] = useState('John');
+    
+    const greeting = useMemo(() => `Hello, ${name}!`,[name]);
+    
+    return (
+        <>
+        <h2>{greeting}</h2>
+        <button onClick={()=>setName('Alex')}>New name</button>
+        </>
+    )
+}
+
+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 locale = 'ru';
-    const messages = messageEn;
-    
 	return (
 		<>
-            <IntlProvider locale={locale} messages={messages}>
-			    <h1><FormattedMessage id='app.welcome' /></h1>
-                <h2><FormattedMessage id='app.userGreeting' values={{ name: <u>Alex</u> }} /></h2>
-                <p><FormattedMessage id='app.notifications' values= {{count: 25}} /></p>
-                <p><FormattedMessage id='app.lastLogin' values={{ date: new Date(), time: new Date()}} /></p>
-                <p><FormattedNumber value={ 999.99 } style='currency' currency='RUB' /></p>
-                <p><FormattedNumber value={0.56} style='percent' /></p>
-                <p><FormattedNumber value={1234.567} minimumFractionDigits={2} maximumFractionDigits={2} /></p>
-                <p><FormattedDate value={new Date()} weekday='long' /></p>
-                <p><FormattedTime value={new Date()} hour='2-digit' minute='2-digit' second='2-digit' /></p>
-                <p><FormattedDateTimeRange from={new Date(2026,6,1,10,0)} to={new Date(2026,6,10,9,0)} /></p>
-            </IntlProvider>
+			{/* Добавьте тестовый контент для проверки */}
+			<h1>Hello, React!</h1>
+            <ParentComponent items={[{name:'Alex'},{name:'Bob'}]} />
 		</>
 	)
 }

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>
 )

src/translations/en.json

@@ -1,6 +0,0 @@
-{
-    "app.welcome": "welcome to React application",
-    "app.userGreeting": "Hello, {name}",
-    "app.notifications": "You have {count, plural, one {# a notification} few {# are notifications} many {# уведомлений} other {# уведомления}}",
-    "app.lastLogin": "Last login was {date,date,long} in {time,time,short}"
-}

src/translations/ru.json

@@ -1,6 +0,0 @@
-{
-    "app.welcome": "добро пожаловать в приложение React",
-    "app.userGreeting": "Здравствуйте, {name}",
-    "app.notifications": "У вас {count, plural, one {# уведомление} few {# уведомления} many {# уведомлений} other {# уведомления}}",
-    "app.lastLogin": "Последний вход был {date,date,long} в {time,time,short}"
-}