以下代码可以优化吗？如果可以请给出优化代码并注释const app = getApp(); function formatDate(date) { const year = date.getFullYear(); const month = date.getMonth() + 1; const day = date.getDate(); return `${year}-${month < 10 ? '0' + month : month}-${day < 10 ? '0' + day : day}`; } Page({ data: { visits: wx.getStorageSync('visits'), dateString: "", current: 0, laifangzongrenshu: "", filteredDataArray: [], }, you: function () { var that = this; var current = that.data.current; if (current < that.data.visits.length - 1) { that.setData({ current: current + 1, }) } let dateString = that.data.dateString; let date = new Date(dateString); date.setDate(date.getDate() + 1); let year = date.getFullYear(); let month = date.getMonth() + 1; let day = date.getDate(); let nextDay = year + '-' + (month < 10 ? '0' + month : month) + '-' + (day < 10 ? '0' + day : day); this.setData({ dateString: nextDay, }); }, zuo: function () { var that = this; var current = that.data.current; if (current > 0) { that.setData({ current: current - 1, }) } let dateString = that.data.dateString; let date = new Date(dateString); date.setDate(date.getDate() - 1); let year = date.getFullYear(); let month = date.getMonth() + 1; let day = date.getDate(); let prevDay = year + '-' + (month < 10 ? '0' + month : month) + '-' + (day < 10 ? '0' + day : day); this.setData({ dateString: prevDay, }); },}）

可以对代码进行如下优化：

const app = getApp();

function formatDate(date) {
  const year = date.getFullYear();
  const month = date.getMonth() + 1;
  const day = date.getDate();
  return `${year}-${month.toString().padStart(2, '0')}-${day.toString().padStart(2, '0')}`;
}

Page({
  data: {
    visits: wx.getStorageSync('visits'),
    dateString: formatDate(new Date()),
    current: 0,
  },

  you() {
    const current = this.data.current;
    if (current < this.data.visits.length - 1) {
      this.setData({
        current: current + 1,
      });
    }
    const dateString = this.data.dateString;
    const nextDate = new Date(new Date(dateString).getTime() + 24 * 60 * 60 * 1000);
    this.setData({
      dateString: formatDate(nextDate),
    });
  },

  zuo() {
    const current = this.data.current;
    if (current > 0) {
      this.setData({
        current: current - 1,
      });
    }
    const dateString = this.data.dateString;
    const prevDate = new Date(new Date(dateString).getTime() - 24 * 60 * 60 * 1000);
    this.setData({
      dateString: formatDate(prevDate),
    });
  },
});

优化思路：

1. 将日期格式化代码封装成一个函数`formatDate`，并使用`padStart`函数补全日期格式中的0。
2. 在`data`中的`dateString`字段中，直接存储格式化后的当天日期，而不是默认为空字符串。
3. 在点击左右按钮时，使用`const`代替`var`，并直接在`setData`中更新数据。
4. 在点击左右按钮时，使用`new Date(dateString)`获取日期对象，而不是使用`new Date()`再转换成日期对象。
5. 在点击左右按钮时，使用`getTime()`获取日期的时间戳，再加上或减去24小时的毫秒数，最后使用`new Date()`将时间戳转换成日期对象。

这样做的好处是，代码更加简洁易读，同时也提高了代码的可维护性。