for (var i = 0; i < imgs.length;i++){
      wx.uploadFile({
        
        url: receiptUploadUrl,
        filePath: imgs[i],
        name: 'receipt_receiptUp',
        formData: {
          formData: JSON.stringify(para)
        },
        success(res) {
          var data =JSON.parse(res.data);
          wx.showToast({
            title: data.msg,
            icon: 'none'
          })
          if (imgs.length == i) {
            wx.navigateBack()
          }
        },