1_counter.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <script src="js/vue.js"></script>
</head>
<body>
  <div id="app"><!--3.用<template>内容代替这里-->
    <xz-counter></xz-counter>
    <xz-counter></xz-counter>
  </div>
  <!--1.1编写组件的HTML模板-->
  <template id="tplCounter">
    <div><!--要求：只能有唯一的父元素-->
      <button @click="change(-1)">-</button><span>{{n}}</span><button @click="change(1)">+</button>
    </div>
  </template>
  <script>//1.2定义组件:监控#tplCounter的HTML内容
    Vue.component("xz-counter",{
      template:"#tplCounter",//代替el
      data(){//data:function(){//变为函数
        return { n:1 }
      },//data:{ n:1 }
      methods:{
        change(i){
          this.n+=i;
          if(this.n<=0) this.n=1;
        }
      }
    })
  </script>
  <script>
    new Vue({ el:"#app" })
  </script>
</body>
</html>