react的hooks的用法详解

// 声明状态
const [ count , setCount ] = useState(0);

// 使用状态
<p>You clicked {count} times</p>
<button onClick={()=>{setCount(count+1)}}>click me</button>

useEffect(()=>{
 console.log("首次渲染与更新")
})

useEffect(()=>{
 console.log("首次渲染与更新")
return ()=>{console.log(首次卸载)}
})

useEffect(()=>{
 console.log("首次渲染与更新")
return ()=>{console.log(首次卸载)}
},[])

useEffect(()=>{
 console.log("首次渲染与更新")
return ()=>{console.log(首次卸载)}
},[num])

const inp = useRef(null)
<input ref={inp}>
//调用
inp.current.value

const onResize = ()=>{setSize({width:xxx,height:xxx})}
 useEffect(()=>{
监听事件 window.addEventListener(“resize”,onResize)
 return 移除监听()=>window.removeEventListener(“resize”,onResize)
 },[])