WXML

<!--control flow-->
<!--This can be used on any type of element-->
<view wx:if="{{boolean==true}}">
    <view class="bg_black"></view>
</view>
<view wx:elif="{{boolean==false}}">
    <view class="bg_red"></view>
</view>
<view wx:else>
    <view class="bg_red"></view>
</view>

Reference

[1] https://blog.csdn.net/u011733020/article/details/108281436