is it not true that the data of the parent component will be affected when the child component of the computing property is changed without the use of the parent-child communication? Why is this child component + 1 and the parent component is still 10? Or is the example I wrote wrong?
<!DOCTYPE html>
<html>
<head>
   <title></title>
   <style type="text/css">
   </style>
   <script src="vue.js"></script>
   <script type="text/javascript">
      window.onload=function(){
         var user={
            template:"-sharpmy_div",
            props:["message"],
            methods:{
              add(){
                this.messagePP;
                this.$emit("increment1");
              }
            }
         }
         new Vue({
               el:"-sharpapp",
               data:{
                test:10
               },
               components:{
                  "user":user
               },
               methods:{
                  incrementTotal: function () {
                      alert(this.test);
                  }
               }
         })
      }
   </script>
</head>
<body>
<template id="my_div">
  <div>
    <h3>{{message}}</h3>
    <button @click=add()></button>
  </div>
</template>
<div id="app">
    <user :message="test" v-on:increment1="incrementTotal"></user>
</div>
</body>
</html>