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import React,{ useState,useRef,useEffect} from "react";function Example () { const [count, setCount] = useState(0); const usePrevious = (value)=> { const ref = useRef() useEffect(() => { ref.current = value }) return ref.current } const previousCount = usePrevious(count); console.log(previousCount, count, '之前的状态和现在的状态') return ()}export default Example{ count}
import React,{ useState,useRef} from "react";function Example () { const [count, setCount] = useState(0); const ref = useRef(0) function handleAlertClick () { setTimeout(() => { console.log(`最新值:${ ref.current}`) console.log(`非最新值:${ count}`); }, 3000) } function increment () { const newCount = count + 1; setCount(newCount) ref.current = newCount } return ()}export default Example{ count}
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