lovecoding
/
Web1020


			
				
					
						
						
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							<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="./js/vue.js"></script>
</head>
<body>
    <div id="app">
        <h1>{{num1}}+{{num2}}={{sum}}</h1>
        <button @click="changeFun">change</button>
    </div>
    <script>
        var app = new Vue({
            el: '#app',
            data:{
                num1:1,
                num2:2,
                sum:0
            },
            methods:{
                changeFun:function(){
                    this.num2 = 100
                }
            },
            watch:{
                num2:function(val,oldVal){
                    // watch 监听num2的变化 接受两个参数 val 代表新值 oldVal 代表旧值
                    console.log(val,oldVal)
                    this.sum = this.num1 + val
                }
            }
        })
    </script>
</body>
</html>