avance
código fuente
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<script>
var date=new Date();
var year=date.getFullYear();
var month=date.getMonth();
var day=date.getDate();
var hour=date.getHours();
var minute=date.getMinutes();
var second=date.getSeconds();
document.write("1.转换大写格式日期模式："+year+"年"+(month+1)+"月"+(day)+"日"+" "+hour+"时"+minute+"分"+second+"秒");
document.write("<br>");
document.write("2.根据日期的不同时间段，做问候语：");
var h=parseInt(hour);
if (h>=8&&h<12){
document.write("早上好！欢迎登陆系统");
}else if (h>=12&&h<14){
document.write("中午好！该休息了");
}else if (h>=14&&h<18){
document.write("下午好！欢迎登陆系统");
}else if (h>=19){
document.write("晚上好！><><><><><><><><");
}
document.write("<br>");
document.write("3.计算当前时间向前、向后（一天、一个月）的日期，并取出时星期几：");
document.write("<br>");
const now=new Date();
const yesterday=new Date(now.setDate(now.getDate()-1));
document.write("向前一天："+yesterday);
document.write("<br>");
const tomorrow=new Date(now.setDate(now.getDate()+2));
document.write("向后一天："+tomorrow);
document.write("<br>");
const lastmonth=new Date(date.setMonth(date.getMonth()-1));
document.write("向前一月："+lastmonth);
document.write("<br>");
const nextmonth=new Date(date.setMonth(date.getMonth()+2));
document.write("向后一月："+nextmonth);
</script>
</body>
</html>