@include ns(dropdown){
  position: relative;
  display: inline-block;
}
@include ns(dropdown-menu){
  position: absolute;
  left: 0;
  z-index: 500;
  padding: 10px 0;
  margin: 5px 0;
  background-color: #fff;
  border: 1px solid #ebeef5;
  border-radius: 4px;
  box-shadow: 0 2px 12px 0 rgba(0, 0, 0, .1);
  li{padding: 0 20px;line-height: 26px;cursor: pointer;white-space: nowrap;
    &:hover{background: #ecf5ff}
  }
  .arrow{
    display: block;
    width: 0;
    height: 0;
    border-bottom: 6px solid #ebeef5;
    border-left: 6px solid transparent;
    border-right: 6px solid transparent;
    position: absolute;left: 45%;top: -6px;
    &:after{
      display: block;
      content: '';
      position: absolute;
      left: -6px;
      top: 1px;
      width: 0;
      height: 0;
      border-bottom: 6px solid #fff;
      border-left: 6px solid transparent;
      border-right: 6px solid transparent;
    }
  }
  &.top{
    bottom: 40px;
    .arrow{
      bottom: -6px;
      top: auto;
      transform: rotate(180deg);
      &:after{
        left: -6px;
        top: auto;
        bottom: -6px;
      }
    }
  }
}
