Vue3 hooks 写法

import { ref, watch } from "vue";
export function useAverage(addNum) {
  const averageNum = ref(0);
  watch(addNum, (addNum) => {
    averageFn(addNum);
  });
  const averageFn = (addNum) => {
    averageNum.value = addNum / 2;
  };
  return {
    averageNum,
    averageFn,
  };
}