alert(getDate()); //当前时间
alert(getDate("day", -2)); //前两天的时间
alert(getDate("day", 2)); //后两天的时间
alert(getDate("month", -2)); //前两个月的时间
alert(getDate("month", 2)); //后两个月的时间
function getDate(type = null, number = 0) {
var nowdate = new Date();
const hours = ('0' + nowdate.getHours()).slice(-2);
const minutes = ('0' + nowdate.getMinutes()).slice(-2);
const seconds = ('0' + nowdate.getSeconds()).slice(-2);
switch (type) {
case "day": //取number天前、后的时间
nowdate.setTime(nowdate.getTime() + (24 * 3600 * 1000) * number);
var y = nowdate.getFullYear();
var m = ('0' + (nowdate.getMonth() + 1)).slice(-2);
var d = ('0' + nowdate.getDate()).slice(-2);
var retrundate = y + '-' + m + '-' + d+" "+hours+":"+minutes+":"+seconds;
break;
case "week": //取number周前、后的时间
var weekdate = new Date(nowdate + (7 * 24 * 3600 * 1000) * number);
var y = weekdate.getFullYear();
var m = ('0' + (nowdate.getMonth() + 1)).slice(-2);
var d = ('0' + nowdate.getDate()).slice(-2);
var retrundate = y + '-' + m + '-' + d+" "+hours+":"+minutes+":"+seconds;
break;
case "month": //取number月前、后的时间
nowdate.setMonth(nowdate.getMonth() + number);
var y = nowdate.getFullYear();
var m = ('0' + (nowdate.getMonth() + 1)).slice(-2);
var d = ('0' + nowdate.getDate()).slice(-2);
var retrundate = y + '-' + m + '-' + d+" "+hours+":"+minutes+":"+seconds;
break;
case "year": //取number年前、后的时间
nowdate.setFullYear(nowdate.getFullYear() + number);
var y = nowdate.getFullYear()...