如何深入理解小程序日历源码的工作机制？

// pages/calendar/calendar.js
Page({
  data: {
    currentYear: 0,
    currentMonth: 0,
    daysInMonth: [],
    weekDays: ['日', '一', '二', '三', '四', '五', '六'],
    today: ''
  },
  onLoad: function (options) {
    const date = new Date();
    this.setData({
      currentYear: date.getFullYear(),
      currentMonth: date.getMonth() + 1,
      today:${date.getFullYear()}${date.getMonth() + 1}${date.getDate()}
    });
    this.generateCalendar(this.data.currentYear, this.data.currentMonth);
  },
  generateCalendar: function (year, month) {
    const firstDay = new Date(year, month  1, 1).getDay();
    const daysInMonth = new Date(year, month, 0).getDate();
    const days = [];
    let day = 1;
    for (let i = 0; i < 6; i++) {
      const week = [];
      for (let j = 0; j < 7; j++) {
        if (i === 0 && j < firstDay || day > daysInMonth) {
          week.push('');
        } else {
          week.push(day);
          day++;
        }
      }
      days.push(week);
    }
    this.setData({
      daysInMonth: days
    });
  },
  changeMonth: function (e) {
    const direction = e.detail.direction;
    let year = this.data.currentYear;
    let month = this.data.currentMonth;
    if (direction === 'left') {
      month;
      if (month === 0) {
        year;
        month = 12;
      }
    } else if (direction === 'right') {
      month++;
      if (month > 12) {
        year++;
        month = 1;
      }
    }
    this.setData({
      currentYear: year,
      currentMonth: month
    });
    this.generateCalendar(year, month);
  }
});

<! pages/calendar/calendar.wxml >
<view class="calendar">
  <view class="header">
    <text class="arrow left" bindtap="changeMonth" datadirection="left">{{currentMonth > 1 ? '上月' : '上一月'}}</text>
    <text class="title">{{{currentYear}}}年{{currentMonth}}月</text>
    <text class="arrow right" bindtap="changeMonth" datadirection="right">{{currentMonth < 12 ? '下月' : '下一月'}}</text>
  </view>
  <view class="weekdays">
    <block wx:for="{{weekDays}}" wx:key="*this">
      <text>{{item}}</text>
    </block>
  </view>
  <view class="days">
    <block wx:for="{{daysInMonth}}" wx:key="*this">
      <view class="week">
        <block wx:for="{{item}}" wx:key="*this">
          <view class="{{['day', {'today': today === currentYear + '' + currentMonth + '' + item}]}}" dataday="{{item}}" bindtap="onDayTap">{{item}}</view>
        </block>
      </view>
    </block>
  </view>
</view>

/* pages/calendar/calendar.wxss */
.calendar {
  display: flex;
  flexdirection: column;
  alignitems: center;
  backgroundcolor: #f5f5f5;
}
.header {
  display: flex;
  justifycontent: spacebetween;
  width: 100%;
  padding: 10px;
  backgroundcolor: #ffffff;
}
.arrow {
  fontsize: 14px;
  color: #999999;
}
.title {
  fontsize: 18px;
  fontweight: bold;
}
.weekdays {
  display: flex;
  justifycontent: spacearound;
  width: 100%;
  padding: 10px;
  backgroundcolor: #ffffff;
}
.days {
  display: flex;
  flexwrap: wrap;
  width: 100%;
}
.week {
  display: flex;
  justifycontent: spacearound;
  width: 100%;
}
.day {
  width: 14.28%;
  height: 30px;
  lineheight: 30px;
  textalign: center;
  border: 1px solid #eeeeee;
  backgroundcolor: #ffffff;
}
.today {
  backgroundcolor: #ffcccc;
}