js realizes the calculation of adding and subtracting months from year to month (pure native realization of the year and month before and after n months of the current year)

1. Not much to say, when you encounter a requirement: let you calculate before or after n months (that is, yyyy-mm + n) of a certain year and month, without plug-ins, are you confused and unable to start? Based on the summary of self-development, we provide you with a solution to achieve this requirement.

       /*
         计算年月加减月份
         originalYtd为String，格式为"yyyy-MM"
         monthNum为Number，格式为n，n为正数表示加月份，为负数表示减月份
       */
   
       function calcMonths(originalYtd, monthNum) {
         let arr = originalYtd.split('-');
         let year = parseInt(arr[0]);
         let month = parseInt(arr[1]);
         month = month + monthNum;
         if (month > 12) {
           let yearNum = parseInt((month - 1) / 12);
           month = month % 12 == 0 ? 12 : month % 12;
           year += yearNum;
         } else if (month <= 0) {
           month = Math.abs(month);
           let yearNum = parseInt((month + 12) / 12);
           let n = month % 12;
           if (n == 0) {
             year -= yearNum;
             month = 12
           } else {
             year -= yearNum;
             month = Math.abs(12 - n)
           }
   
         }
         month = month < 10 ? "0" + month : month;
         return year + "-" + month;
       }

   

    

2. Of course, in addition to the above pure native js implementation, the moment.js plug- in official website portal is a processing method with high frequency and efficiency in actual development. The previous article also taught its use in Vue and summarized nearly 20 common date processing. moment.js usage and summary .
3. The code word is not easy, please ask the big guys from all walks of life to do more and more.