[javascript] How to validate a date?

I'm trying to test to make sure a date is valid in the sense that if someone enters 2/30/2011 then it should be wrong.

How can I do this with any date?

This is ES6 (with let declaration).

function checkExistingDate(year, month, day){ // year, month and day should be numbers
     // months are intended from 1 to 12
    let months31 = [1,3,5,7,8,10,12]; // months with 31 days
    let months30 = [4,6,9,11]; // months with 30 days
    let months28 = [2]; // the only month with 28 days (29 if year isLeap)

    let isLeap = ((year % 4 === 0) && (year % 100 !== 0)) || (year % 400 === 0);

    let valid = (months31.indexOf(month)!==-1 && day <= 31) || (months30.indexOf(month)!==-1 && day <= 30) || (months28.indexOf(month)!==-1 && day <= 28) || (months28.indexOf(month)!==-1 && day <= 29 && isLeap);

    return valid; // it returns true or false
}

In this case I've intended months from 1 to 12. If you prefer or use the 0-11 based model, you can just change the arrays with:

let months31 = [0,2,4,6,7,9,11];
let months30 = [3,5,8,10];
let months28 = [1];

If your date is in form dd/mm/yyyy than you can take off day, month and year function parameters, and do this to retrieve them:

let arrayWithDayMonthYear = myDateInString.split('/');
let year = parseInt(arrayWithDayMonthYear[2]);
let month  = parseInt(arrayWithDayMonthYear[1]);
let day = parseInt(arrayWithDayMonthYear[0]);

function isValidDate(year, month, day) {
        var d = new Date(year, month - 1, day, 0, 0, 0, 0);
        return (!isNaN(d) && (d.getDate() == day && d.getMonth() + 1 == month && d.getYear() == year));
    }

Hi Please find the answer below.this is done by validating the date newly created

var year=2019;
var month=2;
var date=31;
var d = new Date(year, month - 1, date);
if (d.getFullYear() != year
        || d.getMonth() != (month - 1)
        || d.getDate() != date) {
    alert("invalid date");
    return false;
}

Though this was raised long ago, still a most wanted validation. I found an interesting blog with few function.

/* Please use these function to check the reuslt only. do not check for otherewise. other than utiljs_isInvalidDate

Ex:-

utiljs_isFutureDate() retuns only true for future dates. false does not mean it is not future date. it may be an invalid date.

practice :

call utiljs_isInvalidDate first and then use the returned date for utiljs_isFutureDate()

var d = {};

if(!utiljs_isInvalidDate('32/02/2012', d))

if(utiljs_isFutureDate(d))

//date is a future date

else

// date is not a future date



 */

function utiljs_isInvalidDate(dateStr, returnDate) {

    /*dateStr | format should be dd/mm/yyyy, Ex:- 31/10/2017

     *returnDate will be in {date:js date object}.

     *Ex:- if you only need to check whether the date is invalid,

     * utiljs_isInvalidDate('03/03/2017')

     *Ex:- if need the date, if the date is valid,

     * var dt = {};

     * if(!utiljs_isInvalidDate('03/03/2017', dt)){

     *  //you can use dt.date

     * }

     */

    if (!dateStr)
        return true;
    if (!dateStr.substring || !dateStr.length || dateStr.length != 10)
        return true;
    var day = parseInt(dateStr.substring(0, 2), 10);
    var month = parseInt(dateStr.substring(3, 5), 10);
    var year = parseInt(dateStr.substring(6), 10);
    var fullString = dateStr.substring(0, 2) + dateStr.substring(3, 5) + dateStr.substring(6);
    if (null == fullString.match(/^\d+$/)) //to check for whether there are only numbers
        return true;
    var dt = new Date(month + "/" + day + "/" + year);
    if (dt == 'Invalid Date' || isNaN(dt)) { //if the date string is not valid, new Date will create this string instead
        return true;
    }
    if (dt.getFullYear() != year || dt.getMonth() + 1 != month || dt.getDate() != day) //to avoid 31/02/2018 like dates
        return true;
    if (returnDate)
        returnDate.date = dt;
    return false;
}

function utiljs_isFutureDate(dateStrOrObject, returnDate) {
    return utiljs_isFuturePast(dateStrOrObject, returnDate, true);
}

function utiljs_isPastDate(dateStrOrObject, returnDate) {
    return utiljs_isFuturePast(dateStrOrObject, returnDate, false);
}

function utiljs_isValidDateObjectOrDateString(dateStrOrObject, returnDate) { //this is an internal function
    var dt = {};
    if (!dateStrOrObject)
        return false;
    if (typeof dateStrOrObject.getMonth === 'function')
        dt.date = new Date(dateStrOrObject); //to avoid modifying original date
    else if (utiljs_isInvalidDate(dateStrOrObject, dt))
        return false;
    if (returnDate)
        returnDate.date = dt.date;
    return true;

}

function utiljs_isFuturePast(dateStrOrObject, returnDate, isFuture) { //this is an internal function, please use isFutureDate or isPastDate function
    if (!dateStrOrObject)
        return false;
    var dt = {};
    if (!utiljs_isValidDateObjectOrDateString(dateStrOrObject, dt))
        return false;
    today = new Date();
    today.setHours(0, 0, 0, 0);
    if (dt.date)
        dt.date.setHours(0, 0, 0, 0);
    if (returnDate)
        returnDate.date = dt.date;
    //creating new date using only current d/m/y. as td.date is created with string. otherwise same day selection will not be validated.
    if (isFuture && dt.date && dt.date.getTime && dt.date.getTime() > today.getTime()) {
        return true;
    }
    if (!isFuture && dt.date && dt.date.getTime && dt.date.getTime() < today.getTime()) {
        return true;
    }
    return false;
}

function utiljs_isLeapYear(dateStrOrObject, returnDate) {
    var dt = {};
    if (!dateStrOrObject)
        return false;
    if (utiljs_isValidDateObjectOrDateString(dateStrOrObject, dt)) {
        if (returnDate)
            returnDate.date = dt.date;
        return dt.date.getFullYear() % 4 == 0;
    }
    return false;
}

function utiljs_firstDateLaterThanSecond(firstDate, secondDate, returnFirstDate, returnSecondDate) {
    if (!firstDate || !secondDate)
        return false;
    var dt1 = {},
    dt2 = {};
    if (!utiljs_isValidDateObjectOrDateString(firstDate, dt1) || !utiljs_isValidDateObjectOrDateString(secondDate, dt2))
        return false;
    if (returnFirstDate)
        returnFirstDate.date = dt1.date;
    if (returnSecondDate)
        returnSecondDate.date = dt2.date;
    dt1.date.setHours(0, 0, 0, 0);
    dt2.date.setHours(0, 0, 0, 0);
    if (dt1.date.getTime && dt2.date.getTime && dt1.date.getTime() > dt2.date.getTime())
        return true;
    return false;
}

function utiljs_isEqual(firstDate, secondDate, returnFirstDate, returnSecondDate) {
    if (!firstDate || !secondDate)
        return false;
    var dt1 = {},
    dt2 = {};
    if (!utiljs_isValidDateObjectOrDateString(firstDate, dt1) || !utiljs_isValidDateObjectOrDateString(secondDate, dt2))
        return false;
    if (returnFirstDate)
        returnFirstDate.date = dt1.date;
    if (returnSecondDate)
        returnSecondDate.date = dt2.date;
    dt1.date.setHours(0, 0, 0, 0);
    dt2.date.setHours(0, 0, 0, 0);
    if (dt1.date.getTime && dt2.date.getTime && dt1.date.getTime() == dt2.date.getTime())
        return true;
    return false;
}

function utiljs_firstDateEarlierThanSecond(firstDate, secondDate, returnFirstDate, returnSecondDate) {
    if (!firstDate || !secondDate)
        return false;
    var dt1 = {},
    dt2 = {};
    if (!utiljs_isValidDateObjectOrDateString(firstDate, dt1) || !utiljs_isValidDateObjectOrDateString(secondDate, dt2))
        return false;
    if (returnFirstDate)
        returnFirstDate.date = dt1.date;
    if (returnSecondDate)
        returnSecondDate.date = dt2.date;
    dt1.date.setHours(0, 0, 0, 0);
    dt2.date.setHours(0, 0, 0, 0);
    if (dt1.date.getTime && dt2.date.getTime && dt1.date.getTime() < dt2.date.getTime())
        return true;
    return false;
}

copy the whole code into a file and include.

hope this helps.

My function returns true if is a valid date otherwise returns false :D

function isDate  (day, month, year){_x000D_
 if(day == 0 ){_x000D_
  return false;_x000D_
 }_x000D_
 switch(month){_x000D_
  case 1: case 3: case 5: case 7: case 8: case 10: case 12:_x000D_
   if(day > 31)_x000D_
    return false;_x000D_
   return true;_x000D_
  case 2:_x000D_
   if (year % 4 == 0)_x000D_
    if(day > 29){_x000D_
     return false;_x000D_
    }_x000D_
    else{_x000D_
     return true;_x000D_
    }_x000D_
   if(day > 28){_x000D_
    return false;_x000D_
   }_x000D_
   return true;_x000D_
  case 4: case 6: case 9: case 11:_x000D_
   if(day > 30){_x000D_
    return false;_x000D_
   }_x000D_
   return true;_x000D_
  default:_x000D_
   return false;_x000D_
 }_x000D_
}_x000D_
_x000D_
console.log(isDate(30, 5, 2017));_x000D_
console.log(isDate(29, 2, 2016));_x000D_
console.log(isDate(29, 2, 2015));

I just do a remake of RobG solution

var daysInMonth = [31,28,31,30,31,30,31,31,30,31,30,31];
var isLeap = new Date(theYear,1,29).getDate() == 29;

if (isLeap) {
  daysInMonth[1] = 29;
}
return theDay <= daysInMonth[--theMonth]

This solution does not address obvious date validations such as making sure date parts are integers or that date parts comply with obvious validation checks such as the day being greater than 0 and less than 32. This solution assumes that you already have all three date parts (year, month, day) and that each already passes obvious validations. Given these assumptions this method should work for simply checking if the date exists.

For example February 29, 2009 is not a real date but February 29, 2008 is. When you create a new Date object such as February 29, 2009 look what happens (Remember that months start at zero in JavaScript):

console.log(new Date(2009, 1, 29));

The above line outputs: Sun Mar 01 2009 00:00:00 GMT-0800 (PST)

Notice how the date simply gets rolled to the first day of the next month. Assuming you have the other, obvious validations in place, this information can be used to determine if a date is real with the following function (This function allows for non-zero based months for a more convenient input):

var isActualDate = function (month, day, year) {
    var tempDate = new Date(year, --month, day);
    return month === tempDate.getMonth();
};

This isn't a complete solution and doesn't take i18n into account but it could be made more robust.

It's unfortunate that it seems JavaScript has no simple way to validate a date string to these days. This is the simplest way I can think of to parse dates in the format "m/d/yyyy" in modern browsers (that's why it doesn't specify the radix to parseInt, since it should be 10 since ES5):

const dateValidationRegex = /^\d{1,2}\/\d{1,2}\/\d{4}$/;_x000D_
function isValidDate(strDate) {_x000D_
  if (!dateValidationRegex.test(strDate)) return false;_x000D_
  const [m, d, y] = strDate.split('/').map(n => parseInt(n));_x000D_
  return m === new Date(y, m - 1, d).getMonth() + 1;_x000D_
}_x000D_
_x000D_
['10/30/2000abc', '10/30/2000', '1/1/1900', '02/30/2000', '1/1/1/4'].forEach(d => {_x000D_
  console.log(d, isValidDate(d));_x000D_
});

var isDate_ = function(input) {
        var status = false;
        if (!input || input.length <= 0) {
          status = false;
        } else {
          var result = new Date(input);
          if (result == 'Invalid Date') {
            status = false;
          } else {
            status = true;
          }
        }
        return status;
      }

this function returns bool value of whether the input given is a valid date or not. ex:

if(isDate_(var_date)) {
  // statements if the date is valid
} else {
  // statements if not valid
}

I recommend to use moment.js. Only providing date to moment will validate it, no need to pass the dateFormat.

var date = moment("2016-10-19");

And then date.isValid() gives desired result.

Se post HERE

Does first function isValidDate(s) proposed by RobG will work for input string '1/2/'? I think NOT, because the YEAR is not validated ;(

My proposition is to use improved version of this function:

//input in ISO format: yyyy-MM-dd
function DatePicker_IsValidDate(input) {
        var bits = input.split('-');
        var d = new Date(bits[0], bits[1] - 1, bits[2]);
        return d.getFullYear() == bits[0] && (d.getMonth() + 1) == bits[1] && d.getDate() == Number(bits[2]);
}