vue超简选中行改变样式demo

需求：
点击某行，某行应用不同样式
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .active {
            color: red;
        }
    </style>
</head>
<body>
    <div id="app">
        <ul>
            <li v-for = '(i,index) in movies'
            :class = '{active : currentIndex === index}'
            @click = 'btn(index)'
            >{{i}}</li>
            <!-- 把currentindex 和index对比，相同的设置样式 -->
        </ul>
    </div>
    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
    <script>
        const app = new Vue({
            el : '#app',
            data : {
                movies : ['movie1','movie2','movie3','movie4'],
                currentIndex : 2,
                //当前选择是哪一个
            },
            methods :{
                btn(index) {
                    this.currentIndex = index;
                }
            }
        })
    </script>
</body>
</html>