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Detailed explanation of how to perfectly implement JavaScript to return the date of the previous month for a given date
Detailed explanation of how to perfectly implement JavaScript to return the date of the previous month for a given date
这篇文章主要介绍了javascript完美实现给定日期返回上月日期的方法,结合实例形式分析了javascript日期时间的计算技巧,并给出了格式化日期时间的操作方法,需要的朋友可以参考下
本文实例讲述了javascript完美实现给定日期返回上月日期的方法。分享给大家供大家参考，具体如下：
在项目开发中，使用javascript对日期进行处理时，因为在查询中都会有一个初始值，大多都会在当前日期的基础上推一个月，在这种情况下，如果自己写一个，需要考虑的情况较多，在这里给大家分享一下一个比较完善的解决这个问题的方法。供大家参考。例如：给定截止日期enddate=2010-07-31
计算得到开始日期startdate=2010-06-30
这个问题的关键在于对以下几处的考虑：
1、startdate跨年
2、startdate是2月(需考虑闰年的情况)
3、大小月
<html>
<script type="text/javascript">
function getInitStartDate(enddate) {
var comp = enddate.split("-");
var year = comp[0];
var month = comp[1];
var date = comp[2];
if (month == "01") { //前一月跨年
month = 12;
year = year - 1;
} else {
month = month - 1;
if (month == 2 && date > 28) {
date = isLeapYear(year) ? 29 : 28;
} else if (date == 31) {
switch (month) {
case 4:
case 6:
case 9:
case 11:
date = 30;
break;
default:
break;
}
}
}
month = ("" + month).length == 1 ? ("0" + month) : ("" + month);
var dateFormat = year + "-" + month + "-" + date;
return dateFormat;
}
function isLeapYear(y) { //判断y是否为闰年
return (y % 4 == 0) && (y % 400 == 0 || y % 100 != 0);
}
alert(getInitStartDate("2010-07-31"));
</script>
</html>配套给出一个格式化日期的方法：
<script language="JavaScript">
Date.prototype.format = function(format) //author: meizz
{
var o = {
"M+" : this.getMonth()+1, //month
"d+" : this.getDate(), //day
"h+" : this.getHours(), //hour
"m+" : this.getMinutes(), //minute
"s+" : this.getSeconds(), //second
"q+" : Math.floor((this.getMonth()+3)/3), //quarter
"S" : this.getMilliseconds() //millisecond
}
if(/(y+)/.test(format)) format=format.replace(RegExp.$1,
(this.getFullYear()+"").substr(4 - RegExp.$1.length));
for(var k in o)if(new RegExp("("+ k +")").test(format))
format = format.replace(RegExp.$1,
RegExp.$1.length==1 ? o[k] :
("00"+ o[k]).substr((""+ o[k]).length));
return format;
}
alert(new Date().format("yyyy-MM-dd"));
alert(new Date("january 12 2008 11:12:30").format("yyyy-MM-dd hh:mm:ss"));
</script>The above is the detailed content of Detailed explanation of how to perfectly implement JavaScript to return the date of the previous month for a given date. For more information, please follow other related articles on the PHP Chinese website!
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