index.html

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <link  type="text/css" rel="stylesheet" href="./main.css">
    <script src="https://unpkg.com/vue"></script>

    <title>Document</title>
</head>
<body>
<!--vue app是根容器-->
<div id="vue-app">
<button @click="a++">++</button>
    <button @click="b++">---</button>
    <p>a{{a}}</p>
    <p>b{{b}}</p>
    <p>aga+a{{addToA}}}</p>
    <p>age+b{{addToB}}}</p>
</div>
<script src="./app.js"></script>
</body>
</html>

app.js

new Vue({
    el:"#vue-app",
    data:{
        a:0,
        b:0,
        age:20,
    },
    computed:{
        addToA:function (){
            console.log("Add to A")
            return this.a+this.age
        },
        addToB:function (){
            console.log("Add to B")
            return this.a+this.age
        }
    },
    methods:{

     /*   updatexy(event){
            this.x=event.offsetX,
                this.y=event.offsetY
        },
        stopMoving(event){
            event.stopPropagation()
        }*/
    }
})

 运行结果