JavaScript实现给定时间相加天数的方法

/**
* 时间相加处理函数
* @param date 需要计算的时间(xxxx-xx-xx)
* @param plusDays 要加的天数(整数)
*/
function calcuDate(date, plusDays) {
  var dateArray = date.split("-");
  var year = +dateArray[0];
  var month = +dateArray[1];
  var day = +dateArray[2];
  var oriDay = day;
  var secondMonthDays = ((year%4 === 0 && year%100 !== 0) || year%400 === 0) ? 29 : 28;
  while(plusDays>0) {
    oriDay = day
    day += plusDays;
    switch(month) {
      case 4:
      case 6:
      case 9:
      case 11:
        if(day > 30) {
          plusDays -= (30-oriDay)+1;
          month++;
          day = 1;
        } else {
          plusDays = 0;
        }
      break;
      case 2:
        if(day > secondMonthDays) {
          plusDays -= (secondMonthDays-oriDay)+1;
          month++;
          day = 1;
        } else {
          plusDays = 0;
        }
      break;
      default:
        if(day > 31) {
          plusDays -= (31-oriDay)+1;
          day = 1;
          month++;
        } else {
          plusDays = 0;
        }
    }
    if(month>12) {
      month = 1;
      year++;
    }
  }
  return createTimeString(year, month, day);
}