小程序根据返回值是否为空判断标签是否显示

<view class="cu-item" wx:for="{{allSignList}}" wx:key="index">
  <view class="content">
    <view wx:if="{{item.taskReward}}">奖励：{{item.taskReward}}</view>
  </view>
</view>

Page({
  data: {
    allSignList: []
  },
  onLoad: function (options) {
    wx.request({
      url: 'http://www.xxx.com/1.json',
      header: {
        'content-type': 'application/json'
      },
      success: res => {
        this.setData({
           allSignList:res.data.data
        })
      }
    })
  },
})

{
    "msg": "操作成功",
    "code": "0000",
    "data": [
        {
            "taskId": 1,            
            "taskReward": "奖励一个小星星"
        },
        {
            "taskId": 2,
            "taskReward": "奖励一块糖"
        },
        {
            "taskId": 3,           
            "taskReward": ""
        }
    ]
}