获取前一天or后一天的日期
前言：获取前一天or后一天的日期（显示年月日，月或日为个位数的在前面填0）
<!DOCTYPE html>
<html lang="zh">
<head>
<meta charset="UTF-8" />
<title>Document</title>
</head>
<body>
<script>
function formatDateplan() {//返回正常人能看懂的时间
now = new Date();
now.setTime(now.getTime()-24*60*60*1000);//返回昨天的日期
var year = now.getFullYear(),
month = now.getMonth() + 1,
date = now.getDate(),
day = now.getDay(),
hour = now.getHours(),
minute = now.getMinutes(),
second = now.getSeconds();
minute = checkTime(minute);
month = checkTime(month);
date = checkTime(date);
hour = checkTime(hour);
second = checkTime(second);
return year + "-" + month + "-" + date;
// return year + "-" + month + "-" + date + " 星期"+ day +" " + hour + ":" + minute + ":" + second;
// return hour + ":" + minute + ":" + second;
}
function checkTime(i) {
if (i < 10) {
i = "0" + i
}
return i
}
var tm = formatDateplan();
console.log(tm)
</script>
</body>
</html>原理：当前毫秒数减去一天的毫秒数，，，再去获取年月日
1）now.setTime(now.getTime()-24*60*60*1000);//返回昨天的日期
2）now.setTime(now.getTime()+24*60*60*1000);//返回明天的日期
3）去掉这行返回当天的日期
效果：
今天是25号