我在 javascript 中有两个日期：
var first = '2012-11-21';
var second = '2012-11-03';
我想做：
if(first > second){
//...
}
如果没有外部库，最好的方法是什么？
【问题讨论】：
标签： javascript date
if( (new Date(first).getTime() > new Date(second).getTime()))
{
----------------------------------
}
【讨论】：
如果您的日期是严格的yyyy-mm-dd 格式的字符串，如问题所示，那么您的代码将按原样工作，而无需转换为日期对象或数字：
if(first > second){
...将进行字典（即字母数字“字典顺序”）字符串比较 - 它将比较每个字符串的第一个字符，然后是每个字符串的第二个字符，等等。这将给出您想要的结果。 ..
【讨论】：
你可以这样做，它会很好地工作：
var date1 = new Date('2013-07-30');
var date2 = new Date('2013-07-30');
if(date1 === date2){ console.log("both are equal");} //it does not work
==>undefined //result
if(+date1 === +date2){ console.log("both are equal");} //do it this way!
//(use + prefix for a variable that holds a date value)
==> both are equal //result
注意：- 不要忘记使用 + 前缀
【讨论】：
最好的办法是，
var first = '2012-11-21';
var second = '2012-11-03';
if (new Date(first) > new Date(second) {
.....
}
【讨论】：
由于您的日期格式，您可以使用以下代码：
if(parseInt(first.replace(/-/g,""),10) > parseInt(second.replace(/-/g,""),10)){
//...
}
它会检查20121121的数字是否大于20121103。
【讨论】：
replace 将仅替换第一次出现的破折号。
在javascript中使用此函数进行日期比较：
function fn_DateCompare(DateA, DateB) {
var a = new Date(DateA);
var b = new Date(DateB);
var msDateA = Date.UTC(a.getFullYear(), a.getMonth()+1, a.getDate());
var msDateB = Date.UTC(b.getFullYear(), b.getMonth()+1, b.getDate());
if (parseFloat(msDateA) < parseFloat(msDateB))
return -1; // less than
else if (parseFloat(msDateA) == parseFloat(msDateB))
return 0; // equal
else if (parseFloat(msDateA) > parseFloat(msDateB))
return 1; // greater than
else
return null; // error
}
【讨论】：
你也可以这样做。
if (dateFormat(first, "yyyy-mm-dd") > dateFormat(second, "yyyy-mm-dd")) {
console.log("done");
}
或
if (dateFormat(first, "mm-dd-yyyy") > dateFormat(second, "mm-dd-yyyy")) {
console.log("done");
}
我为 dateFormat() 使用以下插件
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);
};
【讨论】：
dateFormat() 函数是什么？