解决手机1像素问题

<div class="tab">
      <div class="tab-item">
        <router-link to="/">商品</router-link>
      </div>
      <div class="tab-item">
        <router-link to="/ratings">评价</router-link>
      </div>
      <div class="tab-item">
        <router-link to="/seller">商家</router-link>
      </div>
    </div>

 .tab {
    display: flex;
    width: %;
    height: px;
    line-height: px;
    border:none;
    position:relative;
  }
  .tab:after{
    content: '';
    position: absolute;
    bottom:;
    left: ;
    background: rgba(, , , );
    width: %;
    height: px;
    -webkit-transform: scaleY();
    transform: scaleY();
    -webkit-transform-origin:  ;
    transform-origin:  ;
  }