vuejs实现标签选项卡动态更改css样式的方法

<ul class="header-list">     <li v-cloak v-for="(item,index) in headerList" v-on:click="selectMainTheme(index)"><a href="java:;" rel="external nofollow" :class="{'active':idx == index}">{{item.name}}</a></li> </ul> 

var app = new Vue({     el:"#app",     router,     data:{       m:"hello vue.js",       active:'2',       idx:'0',  //默认选择首页       headerList:[         {name:'首页1'},         {name:'首页2'},         {name:'首页3'},         {name:'首页4'},         {name:'首页5'},         {name:'首页6'}       ]     },     methods:{       // 1.选择       selectMainTheme:function(index){         console.log("selectMainTheme" + index);         console.log("idx" + this.idx);         this.idx = index;       }       //      }   });