vue17 $watch 监听数据变化

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>智能社——http://www.zhinengshe.com</title>
    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0">
    <meta name="apple-mobile-web-app-capable" content="yes">
    <meta name="apple-mobile-web-app-status-bar-style" content="black">
    <style>
    </style>
    <script src="vue.js"></script>
    <script>
        window.onload=function(){
            var vm=new Vue({
                el:'#box',
                data:{
                    a:111,
                    b:2
                }
            });
            vm.$watch('a',function(){//监听器，a是监听哪个属性变化，
                alert('发生变化了');
                this.b=this.a+100;
            });
            document.onclick=function(){
                vm.a=1;
            };
        };
    </script>
</head>
<body>
    <div id="box">
        {{a}}
        <br>
        {{b}}
    </div>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>智能社——http://www.zhinengshe.com</title>
    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0">
    <meta name="apple-mobile-web-app-capable" content="yes">
    <meta name="apple-mobile-web-app-status-bar-style" content="black">
    <style>
    </style>
    <script src="vue.js"></script>
    <script>
        window.onload=function(){
            var vm=new Vue({
                el:'#box',
                data:{
                    aajson:{name:'strive',age:16},
                    b:2
                }
            });
            vm.$watch('aajson',function(){//不能监听json
                alert('发生变化了');
            });

            document.onclick=function(){
                vm.aajson.name='aaa';
            };
        };
    </script>
</head>
<body>
    <div id="box">
        {{aajson | json}}  <!-- 后面的json是解析成json字符串 -->
        <br>
        {{b}}
    </div>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>智能社——http://www.zhinengshe.com</title>
    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0">
    <meta name="apple-mobile-web-app-capable" content="yes">
    <meta name="apple-mobile-web-app-status-bar-style" content="black">
    <style>

    </style>
    <script src="vue.js"></script>
    <script>

        window.onload=function(){
            var vm=new Vue({
                el:'#box',
                data:{
                    ajson:{name:'strive',age:16},
                    b:2
                }
            });

            vm.$watch('ajson',function(){
                alert('发生变化了');
            },{deep:true});

            document.onclick=function(){
                vm.ajson.name='aaa';
            };
        };

    </script>
</head>
<body>
    <div id="box">
        {{ajson | json}}
        <br>
        {{b}}
    </div>

</body>
</html>