js中日期的加减法

var dateFormat = function () {
var token = /d{1,4}|m{1,4}|yy(?:yy)?|([HhMsTt])1?|[LloSZ]|"[^"]*"|'[^']*'/g,
timezone = /b(?:[PMCEA][SDP]T|(?:Pacific|Mountain|Central|Eastern|Atlantic) (?:Standard|Daylight|Prevailing) Time|(?:GMT|UTC)(?:[-+]d{4})?)b/g,
timezoneClip = /[^-+dA-Z]/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"](),
L = date[_ + "Milliseconds"](),
o = utc ? 0 : date.getTimezoneOffset(),
flags = {
d: d,
dd: pad(d),
ddd: dF.i18n.dayNames[D],
dddd: dF.i18n.dayNames[D + 7],
m: m + 1,
mm: pad(m + 1),
mmm: dF.i18n.monthNames[m],
mmmm: dF.i18n.monthNames[m + 12],
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),
l: pad(L, 3),
L: pad(L > 99 ? Math.round(L / 10) : L),
t: H < 12 ? "a" : "p",
tt: H < 12 ? "am" : "pm",
T: H < 12 ? "A" : "P",
TT: H < 12 ? "AM" : "PM",
Z: utc ? "UTC" : (String(date).match(timezone) || [""]).pop().replace(timezoneClip, ""),
o: (o > 0 ? "-" : "+") + pad(Math.floor(Math.abs(o) / 60) * 100 + Math.abs(o) % 60, 4),
S: ["th", "st", "nd", "rd"][d % 10 > 3 ? 0 : (d % 100 - d % 10 != 10) * d % 10]
};
 
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: [
"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat",
"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"
],
monthNames: [
"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec",
"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"
]
};
 
// For convenience...
Date.prototype.format = function (mask, utc) {
return dateFormat(this, mask, utc);
};

var nowDate = new Date();
//加法操作
var ysDate = new Date(nowDate.getTime()-30*24*60*60*1000).format('yyyy-mm-dd');
//减法操作
var yeDate = new Date(nowDate.getTime()-24*60*60*1000).format('yyyy-m-d');