Webmaster Forum / HTML, CSS, Scripts / JavaScript / April 2006

Matt Kruse is right, the proper way would actually be using the
.valueOf() (or getTime() method of the date object.  This returns the
number of milliseconds from the Unix Epoch (Jan 1st 1970)

Therefore, if a date is more recent, the number of milliseconds would
be high whereas if the date is before the test date, then the number of
millieseconds would be less.

Re-written:
<input type="text" id="timetest" onblur="doDateCheckNow(this);">

function doDateCheckNow(source) {
       var oDate = source;  //dd/mm/yyyy
       var arrDate = oDate.value.split("/");
       var useDate = new Date(arrDate[2], arrDate[1]-1, arrDate[0]);
//yyyy/mm/dd
       var today = new Date();

       if (useDate.valueOf() < today.valueOf())
       {
               alert(useDate+" was before "+today);
       }
       else
       {
               alert(useDate+" will be after "+today);
       }

}

- JS

I was under the (probably mistaken) impression that the explicit conversion
failed in some browser versions for dates, and therefore wasn't good to use.
As this belief goes back a few years, I don't even remember where it
originated.

I've re-written my date code recently to extend Date using prototypes for
most functions. One thing you might not like is that I don't use regular
expressions to parse text. Instead, I still use the manual substring
approach. Someday I'll update it further, but it's solid as-is, and I don't
have a lot of time, so updating working code doesn't seem like the best use
of it :)

I do this in real-time in PHP, actually. I write my code with full comments
and in a style that can be easily reduced. It is then fetched via a PHP
script which either delivers the full code or compacted code. Also, if the
library has any dependencies it can detect this, prepend them into the
source, and deliver a "combined" version. In all my pages and test cases, I
link to the compacted version of the code to make sure that no bugs are
introduced during the compacting.

I also have a fairly extensive set of over 150 test cases at
http://www.javascripttoolbox.com/lib/date/test.php which runs the javascript
in the browser and makes assertions similar to XUnit test suites. It works
well for cross-browser testing of libs like this.

Since you read offline, I'll paste my source below in case you want to look
at it. I'm always open to suggestions, although I can probably already name
many of the same ones that you might offer ;) Hope the code isn't too long,
and of course beware of wrapping.

/*
Date functions

These functions are used to parse, format, and manipulate Date objects.
See documentation and examples at http://www.JavascriptToolbox.com/lib/date/

*/
Date.$VERSION = 1.01;

// Utility function to append a 0 to single-digit numbers
Date.LZ = function(x) {return(x<0||x>9?"":"0")+x};
// Full month names. Change this for local month names
Date.monthNames = new
Array('January','February','March','April','May','June','July','August','September','October','November','December');
// Month abbreviations. Change this for local month names
Date.monthAbbreviations = new
Array('Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec');
// Full day names. Change this for local month names
Date.dayNames = new
Array('Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday');
// Day abbreviations. Change this for local month names
Date.dayAbbreviations = new
Array('Sun','Mon','Tue','Wed','Thu','Fri','Sat');
// Used for parsing ambiguous dates like 1/2/2000 - default to preferring
'American' format meaning Jan 2.
// Set to false to prefer 'European' format meaning Feb 1
Date.preferAmericanFormat = true;

// If the getFullYear() method is not defined, create it
if (!Date.prototype.getFullYear) {
 Date.prototype.getFullYear = function() { var yy=this.getYear(); return
(yy<1900?yy+1900:yy); }
}

// Parse a string and convert it to a Date object.
// If no format is passed, try a list of common formats.
// If string cannot be parsed, return null.
// Avoids regular expressions to be more portable.
Date.parseString = function(val, format) {
 // If no format is specified, try a few common formats
 if (typeof(format)=="undefined" || format==null || format=="") {
   var generalFormats=new Array('y-M-d','MMM d, y','MMM
d,y','y-MMM-d','d-MMM-y','MMM d','MMM-d','d-MMM');
   var monthFirst=new Array('M/d/y','M-d-y','M.d.y','M/d','M-d');
   var dateFirst =new Array('d/M/y','d-M-y','d.M.y','d/M','d-M');
   var checkList=new
Array(generalFormats,Date.preferAmericanFormat?monthFirst:dateFirst,Date.preferAmericanFormat?dateFirst:monthFirst);
   for (var i=0; i<checkList.length; i++) {
     var l=checkList[i];
     for (var j=0; j<l.length; j++) {
       var d=Date.parseString(val,l[j]);
       if (d!=null) {
         return d;
       }
     }
   }
   return null;
 }

 this.isInteger = function(val) {
   for (var i=0; i < val.length; i++) {
     if ("1234567890".indexOf(val.charAt(i))==-1) {
       return false;
     }
   }
   return true;
 };
 this.getInt = function(str,i,minlength,maxlength) {
   for (var x=maxlength; x>=minlength; x--) {
     var token=str.substring(i,i+x);
     if (token.length < minlength) {
       return null;
     }
     if (this.isInteger(token)) {
       return token;
     }
   }
 return null;
 };
 val=val+"";
 format=format+"";
 var i_val=0;
 var i_format=0;
 var c="";
 var token="";
 var token2="";
 var x,y;
 var year=new Date().getFullYear();
 var month=1;
 var date=1;
 var hh=0;
 var mm=0;
 var ss=0;
 var ampm="";
 while (i_format < format.length) {
   // Get next token from format string
   c=format.charAt(i_format);
   token="";
   while ((format.charAt(i_format)==c) && (i_format < format.length)) {
     token += format.charAt(i_format++);
   }
   // Extract contents of value based on format token
   if (token=="yyyy" || token=="yy" || token=="y") {
     if (token=="yyyy") {
       x=4;y=4;
     }
     if (token=="yy") {
       x=2;y=2;
     }
     if (token=="y") {
       x=2;y=4;
     }
     year=this.getInt(val,i_val,x,y);
     if (year==null) {
       return null;
     }
     i_val += year.length;
     if (year.length==2) {
       if (year > 70) {
         year=1900+(year-0);
       }
       else {
         year=2000+(year-0);
       }
     }
   }
   else if (token=="MMM" || token=="NNN"){
     month=0;
     var names =
(token=="MMM"?(Date.monthNames.concat(Date.monthAbbreviations)):Date.monthAbbreviations);
     for (var i=0; i<names.length; i++) {
       var month_name=names[i];
       if
(val.substring(i_val,i_val+month_name.length).toLowerCase()==month_name.toLowerCase())
{
         month=(i%12)+1;
         i_val += month_name.length;
         break;
       }
     }
     if ((month < 1)||(month>12)){
       return null;
     }
   }
   else if (token=="EE"||token=="E"){
     var names = (token=="EE"?Date.dayNames:Date.dayAbbreviations);
     for (var i=0; i<names.length; i++) {
       var day_name=names[i];
       if
(val.substring(i_val,i_val+day_name.length).toLowerCase()==day_name.toLowerCase())
{
         i_val += day_name.length;
         break;
       }
     }
   }
   else if (token=="MM"||token=="M") {
     month=this.getInt(val,i_val,token.length,2);
     if(month==null||(month<1)||(month>12)){
       return null;
     }
     i_val+=month.length;
   }
   else if (token=="dd"||token=="d") {
     date=this.getInt(val,i_val,token.length,2);
     if(date==null||(date<1)||(date>31)){
       return null;
     }
     i_val+=date.length;
   }
   else if (token=="hh"||token=="h") {
     hh=this.getInt(val,i_val,token.length,2);
     if(hh==null||(hh<1)||(hh>12)){
       return null;
     }
     i_val+=hh.length;
   }
   else if (token=="HH"||token=="H") {
     hh=this.getInt(val,i_val,token.length,2);
     if(hh==null||(hh<0)||(hh>23)){
       return null;
     }
     i_val+=hh.length;
   }
   else if (token=="KK"||token=="K") {
     hh=this.getInt(val,i_val,token.length,2);
     if(hh==null||(hh<0)||(hh>11)){
       return null;
     }
     i_val+=hh.length;
     hh++;
   }
   else if (token=="kk"||token=="k") {
     hh=this.getInt(val,i_val,token.length,2);
     if(hh==null||(hh<1)||(hh>24)){
       return null;
     }
     i_val+=hh.length;
     hh--;
   }
   else if (token=="mm"||token=="m") {
     mm=this.getInt(val,i_val,token.length,2);
     if(mm==null||(mm<0)||(mm>59)){
       return null;
     }
     i_val+=mm.length;
   }
   else if (token=="ss"||token=="s") {
     ss=this.getInt(val,i_val,token.length,2);
     if(ss==null||(ss<0)||(ss>59)){
       return null;
     }
     i_val+=ss.length;
   }
   else if (token=="a") {
     if (val.substring(i_val,i_val+2).toLowerCase()=="am") {
       ampm="AM";
     }
     else if (val.substring(i_val,i_val+2).toLowerCase()=="pm") {
       ampm="PM";
     }
     else {
       return null;
     }
     i_val+=2;
   }
   else {
     if (val.substring(i_val,i_val+token.length)!=token) {
       return null;
     }
     else {
       i_val+=token.length;
     }
   }
 }
 // If there are any trailing characters left in the value, it doesn't
match
 if (i_val != val.length) {
   return null;
 }
 // Is date valid for month?
 if (month==2) {
   // Check for leap year
   if ( ( (year%4==0)&&(year%100 != 0) ) || (year%400==0) ) { // leap year
     if (date > 29){
       return null;
     }
   }
   else {
     if (date > 28) {
       return null;
     }
   }
 }
 if ((month==4)||(month==6)||(month==9)||(month==11)) {
   if (date > 30) {
     return null;
   }
 }
 // Correct hours value
 if (hh<12 && ampm=="PM") {
   hh=hh-0+12;
 }
 else if (hh>11 && ampm=="AM") {
   hh-=12;
 }
 return new Date(year,month-1,date,hh,mm,ss);
}

// Check if a date string is valid
Date.isValid = function(val,format) {
 return (Date.parseString(val,format) != null);
}

// Check if a date object is before another date object
Date.prototype.isBefore = function(date2) {
 if (date2==null) {
   return false;
 }
 return (this.getTime()<date2.getTime());
}

// Check if a date object is after another date object
Date.prototype.isAfter = function(date2) {
 if (date2==null) {
   return false;
 }
 return (this.getTime()>date2.getTime());
}

// Check if two date objects have equal dates and times
Date.prototype.equals = function(date2) {
 if (date2==null) {
   return false;
 }
 return (this.getTime()==date2.getTime());
}

// Check if two date objects have equal dates, disregarding times
Date.prototype.equalsIgnoreTime = function(date2) {
 if (date2==null) {
   return false;
 }
 var d1 = new Date(this.getTime()).clearTime();
 var d2 = new Date(date2.getTime()).clearTime();
 return (d1.getTime()==d2.getTime());
}

// Format a date into a string using a given format string
Date.prototype.format = function(format) {
 format=format+"";
 var result="";
 var i_format=0;
 var c="";
 var token="";
 var y=this.getYear()+"";
 var M=this.getMonth()+1;
 var d=this.getDate();
 var E=this.getDay();
 var H=this.getHours();
 var m=this.getMinutes();
 var s=this.getSeconds();
 var yyyy,yy,MMM,MM,dd,hh,h,mm,ss,ampm,HH,H,KK,K,kk,k;
 // Convert real date parts into formatted versions
 var value=new Object();
 if (y.length < 4) {
   y=""+(+y+1900);
 }
 value["y"]=""+y;
 value["yyyy"]=y;
 value["yy"]=y.substring(2,4);
 value["M"]=M;
 value["MM"]=Date.LZ(M);
 value["MMM"]=Date.monthNames[M-1];
 value["NNN"]=Date.monthAbbreviations[M-1];
 value["d"]=d;
 value["dd"]=Date.LZ(d);
 value["E"]=Date.dayAbbreviations[E];
 value["EE"]=Date.dayNames[E];
 value["H"]=H;
 value["HH"]=Date.LZ(H);
 if (H==0){
   value["h"]=12;
 }
 else if (H>12){
   value["h"]=H-12;
 }
 else {
   value["h"]=H;
 }
 value["hh"]=Date.LZ(value["h"]);
 value["K"]=value["h"]-1;
 value["k"]=value["H"]+1;
 value["KK"]=Date.LZ(value["K"]);
 value["kk"]=Date.LZ(value["k"]);
 if (H > 11) {
   value["a"]="PM";
 }
 else {
   value["a"]="AM";
 }
 value["m"]=m;
 value["mm"]=Date.LZ(m);
 value["s"]=s;
 value["ss"]=Date.LZ(s);
 while (i_format < format.length) {
   c=format.charAt(i_format);
   token="";
   while ((format.charAt(i_format)==c) && (i_format < format.length)) {
     token += format.charAt(i_format++);
   }
   if (value[token] != null) {
     result=result + value[token];
   }
   else {
     result=result + token;
   }
 }
 return result;
}

// Get the full name of the day for a date
Date.prototype.getDayName = function() {
 return Date.dayNames[this.getDay()];
}

// Get the abbreviation of the day for a date
Date.prototype.getDayAbbreviation = function() {
 return Date.dayAbbreviations[this.getDay()];
}

// Get the full name of the month for a date
Date.prototype.getMonthName = function() {
 return Date.monthNames[this.getMonth()];
}

// Get the abbreviation of the month for a date
Date.prototype.getMonthAbbreviation = function() {
 return Date.monthAbbreviations[this.getMonth()];
}

// Clear all time information in a date object
Date.prototype.clearTime = function() {
 this.setHours(0);
 this.setMinutes(0);
 this.setSeconds(0);
 this.setMilliseconds(0);
 return this;
}

// Add an amount of time to a date. Negative numbers can be passed to
subtract time.
Date.prototype.add = function(interval, number) {
 if (typeof(interval)=="undefined" || interval==null ||
typeof(number)=="undefined" || number==null) {
   return this;
 }
 number = +number;
 if (interval=='y') { // year
   this.setFullYear(this.getFullYear()+number);
 }
 else if (interval=='M') { // Month
   this.setMonth(this.getMonth()+number);
 }
 else if (interval=='d') { // Day
   this.setDate(this.getDate()+number);
 }
 else if (interval=='w') { // Weekday
   var step = (number>0)?1:-1;
   while (number!=0) {
     this.add('d',step);
     while(this.getDay()==0 || this.getDay()==6) {
       this.add('d',step);
     }
     number -= step;
   }
 }
 else if (interval=='h') { // Hour
   this.setHours(this.getHours() + number);
 }
 else if (interval=='m') { // Minute
   this.setMinutes(this.getMinutes() + number);
 }
 else if (interval=='s') { // Second
   this.setSeconds(this.getSeconds() + number);
 }
 return this;
}