javascript - 用javascript比较日期

Question

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？

Answer 1

if( (new Date(first).getTime() > new Date(second).getTime()))
{
    ----------------------------------
}

Answer 2

如果您的日期是严格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。这将给出你想要的结果......

Answer 3

你可以这样做，它会正常工作：

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

Answer 4

最好的办法是，

var first = '2012-11-21';
var second = '2012-11-03';

if (new Date(first) > new Date(second) {
    .....
}

Answer 5

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)){
   //...
}

它将检查20121121数字是否大于20121103或不大于。

Answer 6

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
  }

Answer 7

你也可以这样做。

if (dateFormat(first, "yyyy-mm-dd") > dateFormat(second, "yyyy-mm-dd")) {
        console.log("done");
}

或者

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);
    };