<!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></title>
    <script src="../js/vue.js"></script>
    <style>
        .v-leave-to{
            opacity: 0;
        }

        .v-enter-form{
            opacity: 0;
        }

        .v-leave-active,
        .v-enter-active{
            transition: opacity 3s ease-in;
        }

        .v-leave-from,
        .v-enter-to{
            opacity: 1;
        }

    </style>

</head>
<body>

    <div id="root"></div>

    <script>  

       const ComponentA = {
        template: `<div> hello word</div>`,
       }

       const ComponentB = {
        template: `<div> bye word</div>`,  
       }

       var app = Vue.createApp({
            data(){ return { component:'component-a' }  },
            methods:{
                handleClick(){
                    if(this.component === 'component-a'){
                        this.component = 'component-b'
                    }else{
                        this.component = 'component-a'
                    }
                }
            },
            components:{
                'component-a': ComponentA,
                'component-b': ComponentB
            },
            template:`
                <transition mode="out-in" appear>
                    <component-a :is ="component" />  
                </transition>
                <button @click="handleClick">切换</button>    
            `,  
        }).mount('#root')    

    </script>

</body>
</html>