Compare commits
3 Commits
| Author | SHA1 | Date | |
|---|---|---|---|
| 6827c800f1 | |||
| 5ee1bf2eee | |||
| c137c644e3 |
+44
-68
@@ -1,82 +1,58 @@
|
||||
import memo, { useMemo, useCallback, useState } from 'react'
|
||||
import React from 'react'
|
||||
|
||||
function MyComponent() {
|
||||
const [count, setCount] = useState(0);
|
||||
const [name, setName] = useState('John');
|
||||
class RandomUser extends React.Component {
|
||||
constructor(props) {
|
||||
super(props)
|
||||
this.state = { user: {} }
|
||||
}
|
||||
|
||||
const greeting = useMemo(() => `Hello, ${name}!`,[name]);
|
||||
componentDidMount() {
|
||||
fetch('https://randomuser.me/api')
|
||||
.then(responce => responce.json())
|
||||
.then(json => this.setState({ user: json.results[0] }));
|
||||
console.log('смонтирован')
|
||||
}
|
||||
|
||||
return (
|
||||
componentDidUpdate(prevProps,prevState) {
|
||||
console.log(this.state);
|
||||
console.log('Компонент обнвлен')
|
||||
}
|
||||
|
||||
componentWillUnmount() {
|
||||
console.log('Компонент таймера размонтирован')
|
||||
}
|
||||
|
||||
render() {
|
||||
return <div>
|
||||
{this.state.user &&
|
||||
this.state.user.name &&
|
||||
(
|
||||
<>
|
||||
<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>
|
||||
</>))}
|
||||
<h2>{this.state.user.name.first} {this.state.user.name.last}</h2>
|
||||
<img src={this.state.user.picture.medium} />
|
||||
<button onClick={() => {
|
||||
console.log('Загружаем ... ')
|
||||
fetch('https://randomuser.me/api')
|
||||
.then(responce => responce.json())
|
||||
.then(json => this.setState({ user: json.results[0] }));
|
||||
}}>Загрузить нового</button>
|
||||
</>
|
||||
)
|
||||
}
|
||||
</div>
|
||||
}
|
||||
}
|
||||
|
||||
function App() {
|
||||
const [showClock, setShowClock] = React.useState(true);
|
||||
|
||||
return (
|
||||
<>
|
||||
{/* Добавьте тестовый контент для проверки */}
|
||||
<h1>Hello, React!</h1>
|
||||
<ParentComponent items={[{name:'Alex'},{name:'Bob'}]} />
|
||||
<h1>Домашнее задание: жизненый цикл</h1>
|
||||
<button onClick={()=> setShowClock(!showClock)}>
|
||||
{showClock ? 'Скрыть часы' : 'Показать часы' }
|
||||
</button>
|
||||
{showClock && <RandomUser />}
|
||||
</>
|
||||
)
|
||||
}
|
||||
|
||||
Reference in New Issue
Block a user