import React, { useCallback, useEffect, useLayoutEffect, useMemo, useState} from "react";

let set = new Set()

function StateFunction() {

    const [value, setValue] = useState(100)

    const [num, setNum] = useState(1)

   const getNumberCallBack = useCallback(function() {

        console.log('num值不变===', num, num*2)  // 输出了两遍

        return num * 2

    }, [num])

    set.add(getNumberCallBack)

    console.log('set=====', set.size, set)

    return <div onClick={() => setValue(value + 1)}>

        这是一个函数组件----

        {'getNumberCallBack====' + getNumberCallBack()}

    </div>