Calculator/pages/index/index.wxml

<!--index.wxml-->
<view class="container">

    <!-- screen -->
    <view class="screen">
        <view plain="true" wx:for-items="{{lines}}" wx:for-index="idx" wx:for-item="line" wx:key="unique">
            <button wx:if="{{idx == 4}}" class="current" plain="true">{{line}}</button>
            <button wx:else plain="true">{{line}}</button>
        </view>
    </view>

    <!-- keyboard -->
    <view class="keyboard">
        <view class="key-rows" wx:for-items="{{layout}}" wx:for-item="itemName" wx:key="unique">
            <view class="key" wx:for-items="{{itemName}}" wx:for-index="id" wx:for-item="keyInfo" wx:key="unique">
                <button bindtap="{{keyInfo.opt}}" id="{{keyInfo.id}}" type="{{keyInfo.type}}">{{keyInfo.value}}</button>
            </view>
        </view>
    </view>

</view>