javascript指定日期增加自然月份（有闰年2月判断）

// An highlighted block
/**
 * 当前日期增加n月
 * @param dateStr 当前日期
 * @param num 月
 * @param type 0:2022-05-30   1：2022-05-30 11:11:11
 * @returns {string}
 */
function commonAddMouth(dateStr,num,type) {
	var monthnum = 0;
	if (typeof (num) == "string"){
		monthnum = parseInt(num);
	}else{
		monthnum = num;
	}
	var date= new Date(dateStr);
	//获取原日
	var day = date.getDate();
	//获取原月份
	var month=date.getMonth();
	//设置增加月份
	date.setMonth(date.getMonth() + (monthnum*1), 1);
	//获取增加的后的月份
	var Jmonth = date.getMonth()+1;
	//获取增加的后的年份
	var Jyear=date.getFullYear();
	if(Jmonth == 4 || Jmonth == 6 || Jmonth == 9 || Jmonth == 11) {
		//小月
		if (day > 30) {
			day = 30;
		}
	}else if (Jmonth == 2) {
		//2月判断是否闰年
		if(((Jyear % 4) == 0) && ((Jyear % 100) != 0) || ((Jyear % 400) == 0)){
			if (day > 29) {
				day = 29;
			} else {
				day = 28;
			}
		}
		if (day > 28) {
			day = 28
		}

	}else{
		//大月
		if (day > 31) {
			day = 31;
		}
	}
	var tHours = date.getHours();
	var tMinutes = date.getMinutes();
	var tSeconds = date.getSeconds();
	Jmonth = doHandleMonth(Jmonth);
	day = doHandleMonth(day);
	if(type=="0"){
		return Jyear+"-"+Jmonth+"-"+day;
	}
	return Jyear+"-"+Jmonth+"-"+day+" "+tHours+":"+tMinutes+":"+tSeconds;
}



/**
 *  日或月补0
 * @param month
 * @returns {string}
 */
function doHandleMonth(month){
	var m = month;
	if(month.toString().length == 1){
		m = "0" + month;
	}
	return m;
}