js计算过去和未来的时间距离现在多少天？

向右看齐 2022-12-28 07:23 186阅读 0赞

/** * 计算过去和未来的时间距离现在多少天？ * 格式 getBeforeDate('2015,5,20') */
    function getBeforeDate(n){ 
      let now = new Date();
      let aftertime = new Date(n);
      let year = now.getFullYear();
      let mon= now.getMonth()+1;
      let day= now.getDate();
      let year_after = aftertime.getFullYear();
      let mon_after = aftertime.getMonth()+1;
      let day_after = aftertime.getDate();
      let chs = 0;
      //获取当月的天数
      function DayNumOfMonth(Year,Month)
      { 
        return 32 - new Date(Year,Month-1,32).getDate();
      }
      if(aftertime.getTime() - now.getTime() < 0){ 
        let temp1 = day_after;
        let temp2 = mon_after;
        let temp3 = year_after;
        day_after = day;
        mon_after = mon;
        year_after = year;
        day = temp1;
        mon = temp2;
        year = temp3;
      }
      if(year == year_after){ //不跨年
        if(mon == mon_after){ //不跨年不跨月
          chs += day_after-day;
        }else{ //不跨年跨月
          chs += DayNumOfMonth(year,mon)- day+1;//加上第一个不满的
          for(let i=1;i< mon_after-mon;i++){ 
            chs += DayNumOfMonth(year,mon+i);
          }
          chs += day_after-1;//加上
        }
      }else{ //存在跨年
        chs += DayNumOfMonth(year,mon)- day+1;//加上开始年份不满的一个月
        for(let m=1;m<12-mon;m++){ 
          chs += DayNumOfMonth(year,mon+m);
        }
        for(let j=1;j < year_after-year;j++){ 
          if((year+j)%400 == 0 || (year+j)%4 == 0 && (year+j)%100 != 0){ 
            chs += 366;
          }else{ 
            chs += 365;
          }
        }
        for(let n=1;n <= mon_after;n++){ 
          chs += DayNumOfMonth(year_after,n);
        }
        chs += day_after-1;
      }
      if(aftertime.getTime() - now.getTime() < 0){ 
        return -chs;
      }else{ 
        return chs;
      }
    }