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 stringsdateFormat.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 stringsdateFormat.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');