<view class="section">
 <view class="section__title">flex-direction: row</view>
 <view class="flex-wrp" style="flex-direction:row;">
  <view class="flex-item bc_green">1</view>
  <view class="flex-item bc_red">2</view>
  <view class="flex-item bc_blue">3</view>
 </view>
</view>
<view class="section">
 <view class="section__title">flex-direction: column</view>
 <view class="flex-wrp" style="height: 300px;flex-direction:column;">
  <view class="flex-item bc_green">1</view>
  <view class="flex-item bc_red">2</view>
  <view class="flex-item bc_blue">3</view>
 </view>
</view>