2.Vue学习：data数据

    <div id="first">
        {{ message }}
        <h2> {{ student.name }} </h2>
        <ul>
            <li> {{ city[0] }} </li>
        </ul>
    </div>

    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
    <script>
        var app = new Vue({
            el: '#first',
            data: {
                message: 'hello word!',
                student: {
                    name: '张三',
                    age: 10,
                    hobby: 'ball'
                },
                city: ['上海', '广州', '北京']
            }
        })
    </script>