日期增加减少

function addDate(date, days) {
var d = new Date(date);
d.setDate(d.getDate() + days);
var month = d.getMonth() + 1;
var day = d.getDate();
if (month < 10) {
month = "0" + month;
}
if (day < 10) {
day = "0" + day;
}
var val = d.getFullYear() + "-" + month + "-" + day;
return val;
}