此方法用於wx自帶的上傳圖片，然後刪除圖片的場景

deleteImg: function(param) {
  var index = param.currentTarget.dataset.index;
  console.log(index);
  var that = this;
    wx.showModal({
    title: '提示',
    content: '要刪除這張照片嗎?',
    success: function(res) {
      if (res.confirm) {
        console.log('使用者點選確定');
        var newPic = that.data.pics;
        var picsArr = that.data.picsArr;
        newPic.splice(index, 1);
        picsArr.splice(index, 1);
        that .setData({
          pics: newPic,
          picsArr: picsArr
        })
      } else {
        console.log('使用者點選取消')
      }
    }
  })
},