[wechat applet] lunar calendar and Gregorian calendar are mutually converted

Source of demand

I wrote an article to get the lunar calendar date before ,【 Wechat applet 】 Get lunar calendar and week , Later, I thought of this small program 【TimeAssistant】 Medium “ Stay away from work ” Functional modules have to be optimized , The specific function interface is shown in the figure below

The original method of this function is to write the holiday date in the code , It's very inflexible to do so , The version must be updated at least once a year , If you can get this date dynamically , Wouldn't it be better .
Considering that these festivals are related to the lunar calendar , Like the Mid Autumn Festival 、 Dragon Boat Festival 、 Spring Festival , So I thought of writing a method , Pass in the lunar date to get the Gregorian date

Combat code

The core approach

  /** *  Get the Gregorian calendar according to the lunar calendar  * @see https://blog.csdn.net/zhangjiaqianghh/article/details/115478404 * @param { Lunar date , 2022-01-01} lunar * @param { Leap month or not , false} leapMonthFlag * @return { Solar date , 2022-02-01} newDate */
const getSolarByLunar = (lunar,leapMonthFlag) => {
    
   //  Use //g Regular replace all 
   var lunarDt = lunar.replace(/-/g,'');
   var lunarYear = parseInt(lunarDt.substring(0, 4));
   var lunarMonth = parseInt(lunarDt.substring(4, 6));
   var lunarDay = parseInt(lunarDt.substring(6, 8));
  
   checkLunarDate(lunarYear, lunarMonth, lunarDay, leapMonthFlag);

   var offset = 0;
   for (var i = 1900; i < lunarYear; i++) {
    
       var yearDaysCount = getYearDays(i); //  Find the number of days in a certain year of the lunar calendar 
       offset += yearDaysCount;
   }

   var leapMonth = getLeapMonth(lunarYear);  

   // There is no leap month in that year, or the month is earlier than the leap month or the month with the same name as the leap month  
   if (leapMonth == 0 || (lunarMonth < leapMonth) || (!leapMonthFlag & lunarMonth == leapMonth)) {
    
     for (var i = 1; i < lunarMonth; i++) {
    
       var tempMonthDaysCount = getMonthDays(lunarYear, i);
       offset += tempMonthDaysCount;
     }
     //  Check whether the date is greater than the maximum day 
     if (lunarDay > getMonthDays(lunarYear, lunarMonth)) {
    
       console.error(' Illegal lunar date ！')
   }
     offset += lunarDay; //  Add the number of days of the month 
   }else{
    
     console.log(" There was a leap month , And the month is later than or equal to the leap month ======" + leapMonth);
     // There was a leap month , And the month is later than or equal to the leap month 
     for (var i = 1; i < lunarMonth; i++) {
    
       var tempMonthDaysCount = getMonthDays(lunarYear, i);
       offset += tempMonthDaysCount;
     }
     if (lunarMonth > leapMonth) {
    
       var temp = getLeapMonthDays(lunarYear); //  Calculate leap month days 
       offset += temp; //  Plus the number of leap months 

       if (lunarDay > getMonthDays(lunarYear, lunarMonth)) {
    
           throw (new Exception(" Illegal lunar date ！"));
       }
       offset += lunarDay;
   } else {
        //  If you need to calculate leap months , You should first add the number of days of the normal month corresponding to the leap month 
       //  The calculation month is leap month 
       var temp = getMonthDays(lunarYear, lunarMonth); //  Calculate the number of non leap months 
       offset += temp;

       if (lunarDay > getLeapMonthDays(lunarYear)) {
    
           throw (new Exception(" Illegal lunar date ！"));
       }
       offset += lunarDay;
     }
   }

   //  Starting point of solar calendar date calculation 
   var startStr = '1900-01-30';
   var newDate =new Date(startStr);
   newDate.setDate(newDate.getDate() + offset);
  // console.log(" test 1======" + getZeroDate(newDate) +getWeekByDate(newDate));
   return newDate;
}

/** *  Get the lunar calendar according to the Gregorian calendar  * @see https://www.iteye.com/blog/lixor-1190599 * @param { The current date } curDate * @returns {int Array  [1,2]} result： Indexes 1 For days , Indexes 2 Represents the month  */
const getLunarBySolar = curDate => {
    
    var leapMonth = 0;
    var date = new Date('1900/1/31');
    //  Find the current time and 1900 year 1 month 31 The number of days between days 
    var offset = parseInt( (curDate.getTime() - date.getTime()) / 86400000 );
    //  use offset Minus the number of days per calendar year , The day of calculation is the day of the lunar calendar ,i The end result is the year of the lunar calendar ,offset It was the first day of the year 
    var iYear, daysOfYear = 0;
    for (iYear = 1900; iYear < 2100 && offset > 0; iYear++) {
    
      daysOfYear = getYearDays(iYear);
      offset -= daysOfYear;
    }
    if (offset < 0) {
    
      offset += daysOfYear;
      iYear--;
    }
    //  Leap which month ,1-12
    leapMonth = getLeapMonth(iYear);
    var leap = false; //  The default value is 
    //  Using the days of the year offset, Subtract each month one by one （ Lunar calendar ） Days of , Find out the day of the month 
    var iMonth, daysOfMonth = 0;
    for (iMonth = 1; iMonth < 13 && offset > 0; iMonth++) {
    
      //  leap month 
      if (leapMonth > 0 && iMonth == (leapMonth + 1) && !leap) {
    
        --iMonth;
        leap = true;
        daysOfMonth = getLeapMonthDays(iYear);
      } else
        daysOfMonth = getMonthDays(iYear, iMonth);

      offset -= daysOfMonth;
      //  Remove leap month 
      if (leap && iMonth == (leapMonth + 1))
        leap = false;
    } 
    // offset by 0 when , And the month just calculated is leap month , To correct 
    if (offset == 0 && leapMonth > 0 && iMonth == leapMonth + 1) {
    
      if (leap) {
    
        leap = false;
      } else {
    
        leap = true;
        --iMonth;
      }
    }
    // offset Less than 0 when , Also need to correct 
    if (offset < 0) {
    
      offset += daysOfMonth;
      --iMonth;
    }
    var result = [];
    result.push(chineseNumber[iMonth - 1]);
    result.push(getChinaDayString(offset + 1));
    return result;
}

Running effect

The following is the measured log diagram of the above two methods

Tool method

1、 Check whether there is a problem with the lunar calendar date

const checkLunarDate = (lunarYear,lunarMonth,lunarDay,leapMonthFlag) =>{
    
  if(lunarYear < 1900 || lunarYear > 2100){
    
    console.error(" Illegal year " + lunarYear);
  }
  if(lunarMonth < 1 ||lunarMonth > 12){
    
    console.error(" Illegal month ======" + lunarMonth);
  }
  if(lunarDay < 1 ||lunarDay > 31){
    
     console.error(" Illegal day ======" + lunarDay);
  }
   // Calculate the leap months of the year 
   var leapMonth = getLeapMonth(lunarYear);  
   if (leapMonthFlag & leapMonth != lunarMonth) {
    
    // console.error(" Non embellish the moon ======");
   }
}

2, Calculate the leap months of the year

const getLeapMonth = year =>{
    
  return (lunarInfo[year - 1900] & 0xf);
}

3, Get the number of days of a month in a leap year

  const getMonthDays = (lunarYeay, month) =>{
    
    if ((month > 31) || (month < 0)) {
    
        throw (new Exception(" The month is wrong ！"));
    }
    // 0X0FFFF[0000 {1111 1111 1111} 1111] middle 12 On behalf of 12 Months ,1 For the moon ,0 For Xiaoyue 
    var bit = 1 << (16 - month);
    if (((lunarInfo[lunarYeay - 1900] & 0x0FFFF) & bit) == 0) {
    
        return 29;
    } else {
    
        return 30;
    }
  }

4, Get leap month days

const getLeapMonthDays = year => {
    
  if (getLeapMonth(year) != 0) {
    
    if ((lunarInfo[year - 1900] & 0xf0000) == 0) {
    
        return 29;
    } else {
    
        return 30;
    }
  } else {
    
    return 0;
  }
}

Other optimization

1, Calculate the day of the week in the Gregorian calendar , Calculate the days of this holiday , For example, Wednesday , It should only last for one day ; If it's Friday or Monday , Then it happened to be last Saturday and Sunday , Although such a calculation method is not very accurate , But you can basically guess

2, Qingming Festival is a special festival , It is not calculated according to the lunar calendar or the Gregorian calendar , But it's basically one of those days every year ; Labor Day is basically 5.1 To 5.5, but 2022 Year is special , from 4.30 Start 5 God , To sum up, it is subject to the announcement made by the holiday office