js根据年月得到当前这个月总共有多少天

let curmonth;
var curDay=this.getday(this.year,this.month);
if(this.month >=10)
{
var curDate = this.year + "-" + this.month + "-" + "01";
var toDate=this.year + "-" + this.month + "-" + curDay;
}
else
{
curmonth= "0"+this.month;
var curDate = this.year + "-" + curmonth + "-" + "01";
var toDate=this.year + "-" + curmonth + "-" + curDay;
}
 

getday(year, month) {
var day = new Date(year, month, 0);
return day.getDate();
},