there are now three files
data.js

import {calNum} from". / Cal" export const a = {name:calNum}

Cal.vue

< script >

const calNum=0

export default {

calNum }

< / script >

test.vue

< template >

<div style="margin-top: 100px">
    <button @click="clickBtn">test</button>
</div> </template>

< script >

import {a} from "./data"
import cal from "./Cal"

export default {

name: "test",
methods:{
  clickBtn(){
    cal.calNumPP
    console.log(cal.calNum)
    console.log(a.name)
  }
}   } </script>

< style scoped >

< / style >

I saved a value in cal and referenced it in data. I set a button in the test interface. Every time I click on the value in cal, the value + 1.
now the test finds out why the value in the output cal can be added by one every time I click, but the value in data is always the initial value.