javascript date format 时间格式函数

如果你的网站需要支持多语言，本地化，那就不可避免的要考虑当地时间的格式，每个国家对时间显示都是不太一样的，比如中文里时间是年月日，而很多欧洲国家是月日年，或者日月年，这里介绍专门处理这个问题的函数：dateFormat

这个函数最重要的就是最后一行的正则表达式，这之前的准备工作包括两步，一步是定义token，另一步是定义通过token要转换的值

/*

* Date Format 1.2.3
* (c) 2007-2009 Steven Levithan <stevenlevithan.com>
* MIT license
*
* Includes enhancements by Scott Trenda <scott.trenda.net>
* and Kris Kowal <cixar.com/~kris.kowal/>
*
* Accepts a date, a mask, or a date and a mask.
* Returns a formatted version of the given date.
* The date defaults to the current date/time.
* The mask defaults to dateFormat.masks.default.
*/


var dateFormat = function () {
var token = /d{1,4}|m{1,4}|yy(?:yy)?|([HhMsTt])\1?|[os]|"[^"]*"|'[^']*'/g,

pad = function (val, len) {
val = String(val);
len = len || 2;
while (val.length < len) val = "0" + val;
return val;
};


// Regexes and supporting functions are cached through closure
return function (date, mask, utc) {
var dF = dateFormat;


// You can't provide utc if you skip other args (use the "UTC:" mask prefix)
if (arguments.length == 1 && Object.prototype.toString.call(date) == "[object String]" && !/\d/.test(date)) {
mask = date;
date = undefined;
}


// Passing date through Date applies Date.parse, if necessary
date = date ? new Date(date) : new Date;
if (isNaN(date)) throw SyntaxError("invalid date");


mask = String(dF.masks[mask] || mask || dF.masks["default"]);


// Allow setting the utc argument via the mask
if (mask.slice(0, 4) == "UTC:") {
mask = mask.slice(4);
utc = true;
}


var _ = utc ? "getUTC" : "get",
d = date[_ + "Date"](),
D = date[_ + "Day"](),
m = date[_ + "Month"](),
y = date[_ + "FullYear"](),
H = date[_ + "Hours"](),
M = date[_ + "Minutes"](),
s = date[_ + "Seconds"](),

flags = {
d: d,
dd: pad(d),
ddd: dF.i18n.dayNames[D].substr(0,3),
dddd: dF.i18n.dayNames[D],
m: m + 1,
mm: pad(m + 1),
mmm: dF.i18n.monthNames[m].substr(0,3),
mmmm: dF.i18n.monthNames[m],
yy: String(y).slice(2),
yyyy: y,
h: H % 12 || 12,
hh: pad(H % 12 || 12),
H: H,
HH: pad(H),
M: M,
MM: pad(M),
s: s,
ss: pad(s),
t: H < 12 ? "a" : "p",
tt: H < 12 ? "am" : "pm",
T: H < 12 ? "A" : "P",
TT: H < 12 ? "AM" : "PM"
};


return mask.replace(token, function ($0) {
return $0 in flags ? flags[$0] : $0.slice(1, $0.length - 1);
});
};
}();


// Some common format strings
dateFormat.masks = {
"default": "ddd mmm dd yyyy HH:MM:ss",
shortDate: "m/d/yy",
mediumDate: "mmm d, yyyy",
longDate: "mmmm d, yyyy",
fullDate: "dddd, mmmm d, yyyy",
shortTime: "h:MM TT",
mediumTime: "h:MM:ss TT",
longTime: "h:MM:ss TT Z",
isoDate: "yyyy-mm-dd",
isoTime: "HH:MM:ss",
isoDateTime: "yyyy-mm-dd'T'HH:MM:ss",
isoUtcDateTime: "UTC:yyyy-mm-dd'T'HH:MM:ss'Z'"
};


// Internationalization strings
dateFormat.i18n = {
dayNames: [
"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"
],
monthNames: [
"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"
]
};


dateFormat(new Date(),'ddd mmm dd yyyy HH:MM:ss')