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; 
      } 
      //  
    }   
});