Cannot get data value within a component in vue-router

when learning the simple example of vue-router, I found that the data data in the component could not be displayed on the page and did not report an error. What is the reason for this?
this is the html file

<body>
    <div id="app">
    <h1>vue-router</h1>
    

<router-link to="/home"></router-link> <router-link to="/pageone">page1</router-link>

<router-view></router-view> </div> </body>

this is the js file

import Vue from "vue"
import VueRouter from "vue-router"
import Home from "./vue/home.vue"
import Pageone from "./vue/pageone.vue"
Vue.use(VueRouter);
const routes=[
    {path:"/home",component:Home},
    {path:"/pageone",component:Pageone}
];
const router=new VueRouter({routes})
const app=new Vue({
    router
}).$mount("-sharpapp")

the two vue files are

home.vue

<template>
<div>{{ msg }}</div>
</template>
export default {
   data () {
    return {
      msg: "home"
    }
  }
}

pageone.vue

<template>
<div>pageone</div>
</template>
export default{
    name:"pageone",
    data(){
    return {
    mag:"pageone"
    }
    }
}

No error is reported in the browser, but it appears as
Click the home page

clipboard.png

page1

clipboard.png

so the data data in home.vue cannot be displayed. What is the problem?

Mar.07,2021

the js section of your vue has not been added

<script>
export default {

}
</script>
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