spring-festival-greetings/utils/lunar.js

/**
 * 农历转换工具
 * 仅包含简单的公历转农历功能
 */

const calendar = {
  /**
   * 农历 1900-2049 的润大小信息表
   * @Array Of Property
   * @return Hex
   */
  lunarInfo: [
    0x04bd8, 0x04ae0, 0x0a570, 0x054d5, 0x0d260, 0x0d950, 0x16554, 0x056a0,
    0x09ad0, 0x055d2, 0x04ae0, 0x0a5b6, 0x0a4d0, 0x0d250, 0x1d255, 0x0b540,
    0x0d6a0, 0x0ada2, 0x095b0, 0x14977, 0x04970, 0x0a4b0, 0x0b4b5, 0x06a50,
    0x06d40, 0x1ab54, 0x02b60, 0x09570, 0x052f2, 0x04970, 0x06566, 0x0d4a0,
    0x0ea50, 0x06e95, 0x05ad0, 0x02b60, 0x186e3, 0x092e0, 0x1c8d7, 0x0c950,
    0x0d4a0, 0x1d8a6, 0x0b550, 0x056a0, 0x1a5b4, 0x025d0, 0x092d0, 0x0d2b2,
    0x0a950, 0x0b557, 0x06ca0, 0x0b550, 0x15355, 0x04da0, 0x0a5d0, 0x14573,
    0x052d0, 0x0a9a8, 0x0e950, 0x06aa0, 0x0aea6, 0x0ab50, 0x04b60, 0x0aae4,
    0x0a570, 0x05260, 0x0f263, 0x0d950, 0x05b57, 0x056a0, 0x096d0, 0x04dd5,
    0x04ad0, 0x0a4d0, 0x0d4d4, 0x0d250, 0x0d558, 0x0b540, 0x0b5a0, 0x195a6,
    0x095b0, 0x049b0, 0x0a974, 0x0a4b0, 0x0b27a, 0x06a50, 0x06d40, 0x0af46,
    0x0ab60, 0x09570, 0x04af5, 0x04970, 0x064b0, 0x074a3, 0x0ea50, 0x06b58,
    0x055c0, 0x0ab60, 0x096d5, 0x092e0, 0x0c960, 0x0d954, 0x0d4a0, 0x0da50,
    0x07552, 0x056a0, 0x0abb7, 0x025d0, 0x092d0, 0x0cab5, 0x0a950, 0x0b4a0,
    0x0baa4, 0x0ad50, 0x055d9, 0x04ba0, 0x0a5b0, 0x15176, 0x052b0, 0x0a930,
    0x07954, 0x06aa0, 0x0ad50, 0x05b52, 0x04b60, 0x0a6e6, 0x0a4e0, 0x0d260,
    0x0ea65, 0x0d530, 0x05aa0, 0x076a3, 0x096d0, 0x04bd7, 0x04ad0, 0x0a4d0,
    0x1d0b6, 0x0d250, 0x0d520, 0x0dd45, 0x0b5a0, 0x056d0, 0x055b2, 0x049b0,
    0x0a577, 0x0a4b0, 0x0aa50, 0x1b255, 0x06d20, 0x0ada0,
  ],

  /**
   * 传回农历 y年的总天数
   * @param y
   * @return Number
   */
  lYearDays: function (y) {
    var i,
      sum = 348;
    for (i = 0x8000; i > 0x8; i >>= 1)
      sum += this.lunarInfo[y - 1900] & i ? 1 : 0;
    return sum + this.leapDays(y);
  },

  /**
   * 传回农历 y年闰月的天数
   * @param y
   * @return Number
   */
  leapDays: function (y) {
    if (this.leapMonth(y)) {
      return this.lunarInfo[y - 1900] & 0x10000 ? 30 : 29;
    }
    return 0;
  },

  /**
   * 传回农历 y年闰哪个月 1-12 , 没闰传回 0
   * @param y
   * @return Number
   */
  leapMonth: function (y) {
    return this.lunarInfo[y - 1900] & 0xf;
  },

  /**
   * 传回农历 y年m月的总天数
   * @param y
   * @param m
   * @return Number
   */
  monthDays: function (y, m) {
    return this.lunarInfo[y - 1900] & (0x10000 >> m) ? 30 : 29;
  },

  /**
   * 算出农历, 传入日期控件, 传回农历日期对象
   * @param objDate
   * @return Object
   */
  solar2lunar: function (objDate) {
    var i,
      temp = 0;
    var baseDate = new Date(1900, 0, 31);
    var offset = Math.floor(
      (objDate.getTime() - baseDate.getTime()) / 86400000,
    );

    var year = 1900;
    for (i = 1900; i < 2050 && offset > 0; i++) {
      temp = this.lYearDays(i);
      if (offset < temp) break;
      offset -= temp;
      year = i;
    }

    // 如果循环结束时 offset 仍大于0 (超出范围)，则年份最后一次增加未被撤销?
    // 不，break时 year=i。 如果没break，year会一直增加。
    // 修正：循环里 year = i 是对的。
    // 但是 calendar.js 原版通常是 year++ 在 check 之后?
    // 这里的逻辑：
    // offset 是总天数。
    // 减去1900年的天数，如果 offset > 0，说明在1900之后。
    // year 变成 1901。
    // 正确。

    var leapMonth = this.leapMonth(year);
    var isLeap = false;
    var month = 1;

    for (i = 1; i < 13; i++) {
      // 闰月
      temp = this.monthDays(year, i);
      if (offset < temp) {
        month = i;
        break;
      }
      offset -= temp;

      if (leapMonth > 0 && i == leapMonth) {
        temp = this.leapDays(year);
        if (offset < temp) {
          isLeap = true;
          month = i;
          break;
        }
        offset -= temp;
      }
    }

    var day = offset + 1;

    // 格式化输出
    const monthCn = this.toChinaMonth(month);
    const dayCn = this.toChinaDay(day);

    return {
      lYear: year,
      lMonth: month,
      lDay: day,
      isLeap: isLeap,
      monthCn: monthCn,
      dayCn: dayCn,
      lunarDateStr: (isLeap ? "闰" : "") + monthCn + dayCn,
    };
  },

  toChinaMonth: function (m) {
    var s = "正二三四五六七八九十冬腊";
    var str = s.substring(m - 1, m);
    return str + "月";
  },

  toChinaDay: function (d) {
    var s = "初十廿三";
    var arr = ["一", "二", "三", "四", "五", "六", "七", "八", "九", "十"];
    var str = "";
    switch (Math.floor(d / 10)) {
      case 0:
        str = "初" + arr[d - 1];
        break;
      case 1:
        str = d == 10 ? "初十" : "十" + arr[d - 11];
        break;
      case 2:
        str = d == 20 ? "二十" : "廿" + arr[d - 21];
        break;
      case 3:
        str = d == 30 ? "三十" : "三" + arr[d - 31];
        break;
    }
    return str;
  },
};

export default calendar;