<!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="https://cdn.bootcss.com/vue/2.6.10/vue.js"></script>
<link href="https://cdn.bootcss.com/twitter-bootstrap/4.3.1/css/bootstrap.css" rel="stylesheet">
</head>
<body>
<div class="container" id='app'>
<H2 v-if = 'flag'> What is the word </ h2>
<button @click='show'>按钮</button>
</div>
<script>
was vm = new Vue ({
el: "#app",
data: {
flag:false
},
methods: {
show(){
this.flag=!this.flag
}
},
});
</script>
</body>
</html>