双大括号，强制数据绑定，绑定事件监听
<!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>Hello World</title>
<script src="../js/vue.js"></script>
</head>
<body>
<div id="app">
<p>用户名: {{username}}</p><!--双大括号-->
<img v-bind:src="imgUrl" alt="logo1"><!--强制数据绑定-->
<img :src="imgUrl" alt="logo2"><!--简写形式-->
<button v-on:click="sayHello">打招呼</button><!--绑定事件监听-->
<button @click="sayHello">打招呼</button><!--简写形式-->
</div>
<script>
// 创建vue实例
const vm = new Vue({// 配置对象
el: '#app',//选择器
data: {//数据：model
username: 'vue',
imgUrl: 'https://cn.vuejs.org/images/logo.svg'
},
methods: {
sayHello(){
alert('hello')
}
}
})
</script>
</body>
</html>