vue单选按钮,选中如何改变其当前按钮颜色

 <span v-for="(item,index) in state" :key="index"
  @click="leftChange(index)" 
  :class="{ liBackground:changeLeftBackground == index}"> {{item}} </span>

  .liBackground {  background: darkcyan; }

 return {
                  changeLeftBackground: 0,    //默认选中第一个
                  state:['兼职','全职','自由职业'],// 模拟数据 所有标签
        }

 methods:{
      leftChange(index) {
              //当前的背景颜色赋给当前点击的索引
             this.changeLeftBackground = index;
       },
}

<ul class="nav nav-tabs" style="background: white;text-align: center">
  <li v-for="(item,index) in tabs" :key="index" class="nav-item">
    <a href="#" rel="external nofollow"  data-toggle="tab" class="nav-link" @click="clickItem(index)" :class="{active:chooseIndex==index}">{{item}}</a>
  </li>
</ul>

tabs: ['BDL', 'EL', 'FL', 'IBL', 'RN', 'WS'],
chooseIndex: 0

clickItem (index) {
  this.chooseIndex = index
  // 点击之后要做的事
}

.nav-tabs{
  list-style: none;
  margin: 0px;
  padding: 0px;
  width: auto;
  overflow: hidden;
}
.nav-item {
  float: left;
  background: #999999;
  width: auto;
  height: 35px;
}
.nav-item a {
  width: 81px;
  height: 35px;
  font-size: 13px;
  line-height: 35px;
  text-decoration: none;
  padding: 11px 34px;
}
.nav-item a:hover, .nav-item a.active {
  background-color: #fafafa;
  color: #000;
}