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JavaScript Date Validation

, 29 Nov 2012 CPOL
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JavaScript Date Validation
For a few days now, I have been battling with the problem of JavaScript date validation. I wanted to validate text inputed by a user as they were typing to tell them if it was a valid date. After much searching on the internet, I found nothing that worked. So I wrote the following code to do the job, it is a simple but effective isDate function:
//Value parameter - required. All other parameters are optional.
function isDate(value, sepVal, dayIdx, monthIdx, yearIdx) {
    try {
        //Change the below values to determine which format of date you wish to check. It is set to dd/mm/yyyy by default.
        var DayIndex = dayIdx !== undefined ? dayIdx : 0; 
        var MonthIndex = monthIdx !== undefined ? monthIdx : 0;
        var YearIndex = yearIdx !== undefined ? yearIdx : 0;
        value = value.replace(/-/g, "/").replace(/\./g, "/"); 
        var SplitValue = value.split(sepVal || "/");
        var OK = true;
        if (!(SplitValue[DayIndex].length == 1 || SplitValue[DayIndex].length == 2)) {
            OK = false;
        if (OK && !(SplitValue[MonthIndex].length == 1 || SplitValue[MonthIndex].length == 2)) {
            OK = false;
        if (OK && SplitValue[YearIndex].length != 4) {
            OK = false;
        if (OK) {
            var Day = parseInt(SplitValue[DayIndex], 10);
            var Month = parseInt(SplitValue[MonthIndex], 10);
            var Year = parseInt(SplitValue[YearIndex], 10);
            if (OK = ((Year > 1900) && (Year < new Date().getFullYear()))) {
                if (OK = (Month <= 12 && Month > 0)) {

                    var LeapYear = (((Year % 4) == 0) && ((Year % 100) != 0) || ((Year % 400) == 0));   
                    if(OK = Day > 0)
                        if (Month == 2) {  
                            OK = LeapYear ? Day <= 29 : Day <= 28;
                        else {
                            if ((Month == 4) || (Month == 6) || (Month == 9) || (Month == 11)) {
                                OK = Day <= 30;
                            else {
                                OK = Day <= 31;
        return OK;
    catch (e) {
        return false;
Just copy the above function and call isDate(value) where value is a string containing a valid or invalid date. The function returns a bool true if the string was a date and false if it wasn't. Hope this helps! " />
EDIT: Thanks to Member 2792937 for bringing a bug to my attention.
Both parseInt('08') and parseInt('09') return zero because the function tries to determine the correct base for the numerical system used. In JavaScript, numbers starting with zero are considered octal and there's no 08 or 09 in octal, hence the problem.
To fix this, just add the second parameter for parseInt, the base to be used for the conversion. The correct calls should be parseInt('08', 10) and parseInt('09', 10).

I have modified my code to fix this issue.

EDIT: Now includes optional parameters for specifying separator value and the indexes. To miss out a parameter simply pass in undefined. Thanks to Lester Callif for the suggestions.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Ed Nutting
United Kingdom United Kingdom

I am Edward Nutting, born March 1996 and I am currently a Computer Science and Electronic Engineering undergraduate at the University of Bristol, UK. I've been self-teaching programming since I was eight years old and have dabbled in many different areas from web development (where I had my own advertising startup) to low level operating system stuff (my current project Fling OS).

The articles and code on this profile are some of my early work (from when I was aged about 13 to 16) but despite my young age, it has been well received by CodeProject users. My more recent work has been for companies or on projects hosted on GitHub, CodePlex or BitBucket.

I keep an eye on many things techy and am open to any and all ideas, so please feel free to contact me if you think I can help! Smile | :)

Ed Nutting

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Comments and Discussions

QuestionBug with year validation Pin
Member 842090121-Nov-11 6:59
memberMember 842090121-Nov-11 6:59 
AnswerRe: Bug with year validation Pin
Edward Nutting21-Nov-11 10:42
memberEdward Nutting21-Nov-11 10:42 

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