Javascript validate date format?

Question

i cant figure out how to check the format of the date, i want it to check that the date is
dd/mm/yy
               if(document.getElementById(i+"eddstartdate").value == ????)
                    window.alert('You Must Enter a Start Date with a valid format');
                    return;
               }

Answer 1

I'm sure I had a small solution to this simple requirement. But I'm pasting the solution below.
Include a js file named as say dateValidate.js with contents below and call the js function isDate(val,format) wherein you pass the value and the required format. Based on the boolean value return show the required message.
var MONTH_NAMES = new Array('January','February','March','April','May','June','July','August','September','October','November','December','Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec');
// isDate ( date_string, format_string )
// Returns true if date string matches format of format string and
// is a valid date. Else returns false.
// It is recommended that you trim whitespace around the value before
// passing it to this function, as whitespace is NOT ignored!
function isDate(val,format) {
     //alert("val="+val)
     var date = getDateFromFormat(val,format);
     //alert("date="+date)
     if (date == 0) { return false; }
     return true;
// compareDates(date1,date1format,date2,date2format)
//   Compare two date strings to see which is greater.
//   Returns:
//   1 if date1 is greater than date2
//   0 if date2 is greater than date1 of if they are the same
//  -1 if either of the dates is in an invalid format
function compareDates(date1,dateformat1,date2,dateformat2) {
     var d1 = getDateFromFormat(date1,dateformat1);
     var d2 = getDateFromFormat(date2,dateformat2);
     if (d1==0 || d2==0) {
          return -1;
     else if (d1 >= d2) {
          return 1;
     return 0;
//      function to alert messages..
/*function warnInvalid(s)
{   alert(s)
    return false
// formatDate (date_object, format)
// Returns a date in the output format specified.
// The format string uses the same abbreviations as in getDateFromFormat()
function formatDate(date,format) {
     format = format+"";
     var result = "";
     var i_format = 0;
     var c = "";
     var token = "";
     var y = date.getYear()+"";
     var M = date.getMonth()+1;
     var d = date.getDate();
     var H = date.getHours();
     var m = date.getMinutes();
     var s = date.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
     // Year
     if (y.length < 4) {
          y = y-0+1900;
     y = ""+y;
     yyyy = y;
     yy = y.substring(2,4);
     // Month
     if (M < 10) { MM = "0"+M; }
          else { MM = M; }
     MMM = MONTH_NAMES[M-1];
     // Date
     if (d < 10) { dd = "0"+d; }
          else { dd = d; }
     // Hour
     h=H+1;
     K=H;
     k=H+1;
     if (h > 12) { h-=12; }
     if (h == 0) { h=12; }
     if (h < 10) { hh = "0"+h; }
          else { hh = h; }
     if (H < 10) { HH = "0"+K; }
          else { HH = H; }
     if (K > 11) { K-=12; }
     if (K < 10) { KK = "0"+K; }
          else { KK = K; }
     if (k < 10) { kk = "0"+k; }
          else { kk = k; }
     // AM/PM
     if (H > 11) { ampm="PM"; }
     else { ampm="AM"; }
     // Minute
     if (m < 10) { mm = "0"+m; }
          else { mm = m; }
     // Second
     if (s < 10) { ss = "0"+s; }
          else { ss = s; }
     // Now put them all into an object!
     var value = new Object();
     value["yyyy"] = yyyy;
     value["yy"] = yy;
     value["y"] = y;
     value["MMM"] = MMM;
     value["MM"] = MM;
     value["M"] = M;
     value["dd"] = dd;
     value["d"] = d;
     value["hh"] = hh;
     value["h"] = h;
     value["HH"] = HH;
     value["H"] = H;
     value["KK"] = KK;
     value["K"] = K;
     value["kk"] = kk;
     value["k"] = k;
     value["mm"] = mm;
     value["m"] = m;
     value["ss"] = ss;
     value["s"] = s;
     value["a"] = 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);
               i_format++;
          if (value[token] != null) {
               result = result + value[token];
          else {
               result = result + token;
     return result;
// Utility functions for parsing in getDateFromFormat()
function _isInteger(val) {
     var digits = "1234567890";
     for (var i=0; i < val.length; i++) {
          if (digits.indexOf(val.charAt(i)) == -1) { return false; }
     return true;
function _getInt(str,i,minlength,maxlength) {
     for (x=maxlength; x>=minlength; x--) {
          var token = str.substring(i,i+x);
          if (token.length < minlength) {
               return null;
          if (_isInteger(token)) {
               return token;
     return null;
// END Utility Functions
// getDateFromFormat( date_string , format_string )
// This function takes a date string and a format string. It matches
// If the date string matches the format string, it returns the
// getTime() of the date. If it does not match, it returns 0.
// This function uses the same format strings as the
// java.text.SimpleDateFormat class, with minor exceptions.
// The format string consists of the following abbreviations:
// Field        | Full Form          | Short Form
// -------------+--------------------+-----------------------
// Year         | yyyy (4 digits)    | yy (2 digits), y (2 or 4 digits)
// Month        | MMM (name or abbr.)| MM (2 digits), M (1 or 2 digits)
// Day of Month | dd (2 digits)      | d (1 or 2 digits)
// Hour (1-12)  | hh (2 digits)      | h (1 or 2 digits)
// Hour (0-23)  | HH (2 digits)      | H (1 or 2 digits)
// Hour (0-11)  | KK (2 digits)      | K (1 or 2 digits)
// Hour (1-24)  | kk (2 digits)      | k (1 or 2 digits)
// Minute       | mm (2 digits)      | m (1 or 2 digits)
// Second       | ss (2 digits)      | s (1 or 2 digits)
// AM/PM        | a                  |
// Examples:
//  "MMM d, y" matches: January 01, 2000
//                      Dec 1, 1900
//                      Nov 20, 00
//  "m/d/yy"   matches: 01/20/00
//                      9/2/00
//  "MMM dd, yyyy hh:mm:ssa" matches: "January 01, 2000 12:30:45AM"
function getDateFromFormat(val,format) {
     var date_split=val.split("/");
     /*if(date_split[0].length<2)
          date_split[0]="0"+date_split[0];
     if(date_split[1].length<2)
          date_split[1]="0"+date_split[1];
     val = date_split[0] + "/" + date_split[1] + "/" + date_split[2];*/
     val = val+"";
     format = format+"";
     var i_val = 0;
     var i_format = 0;
     var c = "";
     var token = "";
     var token2= "";
     var x,y;
     var now   = new Date();
     var year  = now.getYear();
     var month = now.getMonth()+1;
     var date  = now.getDate();
     var hh    = now.getHours();
     var mm    = now.getMinutes();
     var ss    = now.getSeconds();
     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);
               i_format++;
          // Extract contents of value based on format token
          if (token=="yyyy" || token=="yy" || token=="y") {
               if (token=="yyyy") { x=4;y=4; }// 4-digit year
               if (token=="yy")   { x=2;y=2; }// 2-digit year
               if (token=="y")    { x=2;y=4; }// 2-or-4-digit year
               year = _getInt(val,i_val,x,y);
               if (year == null) { return 0; }
               i_val += year.length;
               if (year.length == 2) {
                    if (year > 70) {
                         year = 1900+(year-0);
                    else {
                         year = 2000+(year-0);
          else if (token=="MMM"){// Month name
               month = 0;
               for (var i=0; i<MONTH_NAMES.length; i++) {
                    var month_name = MONTH_NAMES;
                    if (val.substring(i_val,i_val+month_name.length).toLowerCase() == month_name.toLowerCase()) {
                         month = i+1;
                         if (month>12) { month -= 12; }
                         i_val += month_name.length;
                         break;
               if (month == 0) { return 0; }
               if ((month < 1) || (month>12)) { return 0; }
               // TODO: Process Month Name
          else if (token=="MM" || token=="M") {
               x=token.length; y=2;
               month = getInt(val,ival,x,y);
               if (month == null) { return 0; }
               if ((month < 1) || (month > 12)) { return 0; }
               i_val += month.length;
          else if (token=="dd" || token=="d") {
               x=token.length; y=2;
               date = getInt(val,ival,x,y);
               if (date == null) { return 0; }
               if ((date < 1) || (date>31)) { return 0; }
               i_val += date.length;
          else if (token=="hh" || token=="h") {
               x=token.length; y=2;
               hh = getInt(val,ival,x,y);
               if (hh == null) { return 0; }
               if ((hh < 1) || (hh > 12)) { return 0; }
               i_val += hh.length;
               hh--;
          else if (token=="HH" || token=="H") {
               x=token.length; y=2;
               hh = getInt(val,ival,x,y);
               if (hh == null) { return 0; }
               if ((hh < 0) || (hh > 23)) { return 0; }
               i_val += hh.length;
          else if (token=="KK" || token=="K") {
               x=token.length; y=2;
               hh = getInt(val,ival,x,y);
               if (hh == null) { return 0; }
               if ((hh < 0) || (hh > 11)) { return 0; }
               i_val += hh.length;
          else if (token=="kk" || token=="k") {
               x=token.length; y=2;
               hh = getInt(val,ival,x,y);
               if (hh == null) { return 0; }
               if ((hh < 1) || (hh > 24)) { return 0; }
               i_val += hh.length;
               h--;
          else if (token=="mm" || token=="m") {
               x=token.length; y=2;
               mm = getInt(val,ival,x,y);
               if (mm == null) { return 0; }
               if ((mm < 0) || (mm > 59)) { return 0; }
               i_val += mm.length;
          else if (token=="ss" || token=="s") {
               x=token.length; y=2;
               ss = getInt(val,ival,x,y);
               if (ss == null) { return 0; }
               if ((ss < 0) || (ss > 59)) { return 0; }
               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 0;
          else {
               if (val.substring(i_val,i_val+token.length) != token) {
                    return 0;
               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 0;
     // 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 false; }
          else {
               if (date > 28) { return false; }
     if ((month==4)||(month==6)||(month==9)||(month==11)) {
          if (date > 30) { return false; }
     // Correct hours value
     if (hh<12 && ampm=="PM") {
          hh+=12;
     else if (hh>11 && ampm=="AM") {
          hh-=12;
     var newdate = new Date(year,month-1,date,hh,mm,ss);
     return newdate.getTime();
Hope this helps
Regards
Rohit