微信小程序实现tab切换

<view class="menu">
        <view class='{{num==1?"activity":""}}' data-num='1' catchtap="goIndex">评论</view>
        <view class='{{num==2?"activity":""}}' data-num='2' catchtap="goIndex">点赞</view>
    </view>

data:{
     num:1  
}

goIndex: function (e) {
      console.log(e);
      this.setData({
          num: e.target.dataset.num
      })
 },