计算每个月多少天

let date = new Date(time);

let y = date.getFullYear();

let m =date.getMonth()+1;

if(m == 2){

　　return y % 4 == 0 ?time + "-" + 29 : time + "-" + 28;

}else if(m == 1 || m == 3 || m == 5 || m == 7 || m == 8 || m == 10 || m == 12){

　　return time + "-" + 31;

}else{

　　return time + "-" + 30;

}