<!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>
</head>
<style>
    .active {
        color: red;
    }
</style>

<body>
    <div id="app">
        <h2>{{firstName+' '+lastName}}</h2>
        <h2>{{fullname}}</h2>
    </div>
    <script src="./js/vue.js"></script>
    <script>
        var app = new Vue({
            el: '#app',
            data: {
                firstName: '你好',
                lastName: '歌谣'
            },
            methods: {

            },
            computed: {
                fullname: function() {
                    return this.firstName + '' + this.lastName
                }
            }
        })
    </script>
</body>

</html>

运行结果