lovecoding
/
VIP28


			
				
					
						
						
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							<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div id="app">
    <button @click="change()">修改</button>
    <h2>姓: {{firstName}}</h2>
    <h2>名：{{lastName}}</h2>
    <h2>姓名：{{fullName}}</h2>
  </div>
  <script src="./vue.js"></script>
  <script>
    var app = new Vue({
      el: "#app",
      data:{
        firstName: 'zhang',
        lastName: 'san',
        sex: '男'
      },
      computed:{
        fullName: function(){
          console.log(333)
          return this.firstName + this.lastName
        }
      },
      methods:{
        change(){
          this.firstName = 'li'
        }
      },
      watch:{
        firstName: function(){
          console.log(111)
        },
        lastName: function(){
          console.log(222)
        },
        sex: function(){
          console.log(555)
        }
        /* 
        在Vue中 watch和computed都是用来观察数据变化的
        作用不相同

        watch是响应数据变化并且进行相应的操作
        computed是用来计算一些基于响应式数据的操作

        computed是带有一定缓存的  当响应式没有变化的时候
        computed不会重新计算
        
        */
      }
    })
  </script>
</body>
</html>