这路径日期后面显示undefined,求解，这是什么问题？

代码如下：

 //上传图片到云服务器
    const fileIDList=[];
    if(that.data.tempImages.length > 0){
      const today = new Date();
      const year = today.getFullYear();
      const month = today.getMonth() +1;
      const day = today.getDate();
      that.data.tempImages.forEach((value,index) => {
        const cloudPath = "weibos/"+year+"/"+month+"/"+day+"/"+getUUID()+"/"+"."+getExt(value);
        wx.cloud.uploadFile({
          filePath:value,
          cloudPath:cloudPath,
          success:res=>{
            console.log(res);
            // fileIDList.push(res.fileID);
            // if(fileIDList.lenght == that.data.tempImages.lenght){
            //   //接下来就是发布微博了
            //   wx.hideLoading({});
            //   wx.showToast({
            //     title:"图片都上传完成"
            //   })
            // }
          }
        })
      })
    }
  },