<ul class="cssNav">
  <li v-for="(item,i) in list" :class="[num==i?'active':'']" @click="tab(i)">{{item}}</li>
</ul>

.cssNav {
    margin: 100px auto;
    background-color: #dedede;
    width:420px;
  }

  .cssNav li{
    padding:0 20px;
    line-height: 40px;
    background-color: #50abe4;
    display: inline-block;
    color:#fff;
    position: relative;
    margin-right: 4px;
  }
  .cssNav li:after{
    content:"";
    display: block;
    border-top:20px solid transparent;
    border-bottom:20px solid transparent;
    border-left:20px solid #50abe4;
    position: absolute;
    right:-20px;
    top:0;
    z-index: 10;
  }
  .cssNav li:before{
    content:"";
    display: block;
    border-top:20px solid transparent;
    border-bottom:20px solid transparent;
    border-left:20px solid #fff;
    position: absolute;
    left:0px;
    top:0;
  }

  .cssNav li:first-child{
    border-radius: 4px 0 0 4px;
    padding-left:25px;
  }
  .cssNav li:last-child,.cssNavEnd{
    border-radius: 0 4px 4px 0;
    padding-right: 25px;
  }
  .cssNav li:first-child:before{
    display: none;
  }
  .cssNav li:last-child:after,.cssNavEnd:after{
    display: none;
  }
  .cssNav li.active { 
    background-color: #ef72b6; 
  } 
  .cssNav li.active:after { 
    border-left-color: #ef72b6; 
  } 

// 需要引入vue.js 
 new Vue({
    el: '.cssNav',
    data: {
        num:0,
        list:['首頁','測試文字','新聞也','地址頁']
      },
    methods: {
      tab:function(i){
        this.num = i;
      }
    }  
  })