JavaScript has a flaw in its date validation that allows for incorrect dates like 'dd.mm.0302' or '27.08.0974' to pass through

Question

JavaScript has a flaw in its date validation that allows for incorrect dates like 'dd.mm.0302' or '27.08.0974' to pass through

I have encountered an issue with date validation from the database where some years in the date fields appear to be incorrect (such as 28.02.0302). I need to validate these dates properly, but the functions I found online are not working as expected. How can I make them function correctly? Here are the functions I have attempted to use:

function isValidDate(d) {


if ( Object.prototype.toString.call(d) !== "[object Date]" )
    return false;
  return !isNaN(d.getTime());

}

function isValidDate11(s) {
    // format D(D)/M(M)/(YY)YY
    var dateFormat = /^\d{1,4}[\.|\/|-]\d{1,2}[\.|\/|-]\d{1,4}$/;

    if (dateFormat.test(s)) {
        // remove any leading zeros from date values
        s = s.replace(/0*(\d*)/gi,"$1");
        var dateArray = s.split(/[\.|\/|-]/);

        // correct month value
        dateArray[1] = dateArray[1]-1;

        // correct year value
        if (dateArray[2].length<4) {
            // correct year value
            dateArray[2] = (parseInt(dateArray[2]) < 50) ? 2000 + parseInt(dateArray[2]) : 1900 + parseInt(dateArray[2]);
        }

        var testDate = new Date(dateArray[2], dateArray[1], dateArray[0]);
        if (testDate.getDate()!=dateArray[0] || testDate.getMonth()!=dateArray[1] || testDate.getFullYear()!=dateArray[2]) {
            return false;
        } else {
            return true;
        }
    } else {
        return false;
    }
}

javascript validation date

Answer 1

Answer №1

Your script mistakenly changes the date you input as 28.02.0302 to the 28th of February in the year 2202, making it a valid date despite your intended date being different.

There are two specific parts of the script that cause this alteration:

The first part removes any leading zeroes from the date values, transforming the year from 0302 to 302.

// Remove any leading zeros from date values
   s = s.replace(/0*(\d*)/gi,"$1");

The second part checks if the date has less than 4 characters and adds 2000 if it's less than 50 and 1900 if it's more.

// Correct year value
if (dateArray[2].length<4) {
    dateArray[2] = (parseInt(dateArray[2]) < 50) ? 2000 + parseInt(dateArray[2]) : 1900 + parseInt(dateArray[2]);
}

The second part is slightly more complex, likely created to validate dates like 01.01.12 as 01/01/2012 and 01.01.93 as 01/01/1999.

These adjustments are not entirely necessary, and you can modify the function as follows:

function isValidDate11(s) {
    // Format D(D)/M(M)/(YY)YY
    var dateFormat = /^\d{1,4}[\.|\/|-]\d{1,2}[\.|\/|-]\d{1,4}$/;

    if (dateFormat.test(s)) {
        var dateArray = s.split(/[\.|\/|-]/);
        // Correct month value
        dateArray[1] = dateArray[1]-1;

        var testDate = new Date(dateArray[2], dateArray[1], dateArray[0]);

        if (testDate.getDate()!=dateArray[0] || testDate.getMonth()!=dateArray[1] || testDate.getFullYear()!=dateArray[2]) {
            return false;
        } else {
            return true;
       }
   } else {
        return false;
   }
}

Even though the date 28.02.0302 is considered valid due to being checked as the 28th of February in the year 302, it's important to define what you classify as a valid date.

If you encounter issues with dates like 0302, you may prefer a date format with a four-digit year and no leading zero:

function isValidDate11(s) {
    // Format D(D)/M(M)/YYYY
    var dateFormat = /^\d{1,4}[\.|\/|-]\d{1,2}[\.|\/|-]\d{4}$/;

    if (dateFormat.test(s)) {
        // Remove any leading zeros from date values
        s = s.replace(/0*(\d*)/gi,"$1");
        var dateArray = s.split(/[\.|\/|-]/);
        // Correct month value
        dateArray[1] = dateArray[1]-1;

        if(dateArray[2].length != 4){
          return false;
        }

        var testDate = new Date(dateArray[2], dateArray[1], dateArray[0]);

        if (testDate.getDate()!=dateArray[0] || testDate.getMonth()!=dateArray[1] || testDate.getFullYear()!=dateArray[2]) {
            return false;
        } else {
            return true;
        }
    } else {
        return false;
    }
}

This adjustment will resolve the issue with the 0302 year problem but may not work for dates ending with a two-digit year like .14.

Answer 2

Your script mistakenly changes the date you input as 28.02.0302 to the 28th of February in the year 2202, making it a valid date despite your intended date being different.

There are two specific parts of the script that cause this alteration:

The first part removes any leading zeroes from the date values, transforming the year from 0302 to 302.

// Remove any leading zeros from date values
   s = s.replace(/0*(\d*)/gi,"$1");

The second part checks if the date has less than 4 characters and adds 2000 if it's less than 50 and 1900 if it's more.

// Correct year value
if (dateArray[2].length<4) {
    dateArray[2] = (parseInt(dateArray[2]) < 50) ? 2000 + parseInt(dateArray[2]) : 1900 + parseInt(dateArray[2]);
}

The second part is slightly more complex, likely created to validate dates like 01.01.12 as 01/01/2012 and 01.01.93 as 01/01/1999.

These adjustments are not entirely necessary, and you can modify the function as follows:

function isValidDate11(s) {
    // Format D(D)/M(M)/(YY)YY
    var dateFormat = /^\d{1,4}[\.|\/|-]\d{1,2}[\.|\/|-]\d{1,4}$/;

    if (dateFormat.test(s)) {
        var dateArray = s.split(/[\.|\/|-]/);
        // Correct month value
        dateArray[1] = dateArray[1]-1;

        var testDate = new Date(dateArray[2], dateArray[1], dateArray[0]);

        if (testDate.getDate()!=dateArray[0] || testDate.getMonth()!=dateArray[1] || testDate.getFullYear()!=dateArray[2]) {
            return false;
        } else {
            return true;
       }
   } else {
        return false;
   }
}

Even though the date 28.02.0302 is considered valid due to being checked as the 28th of February in the year 302, it's important to define what you classify as a valid date.

If you encounter issues with dates like 0302, you may prefer a date format with a four-digit year and no leading zero:

function isValidDate11(s) {
    // Format D(D)/M(M)/YYYY
    var dateFormat = /^\d{1,4}[\.|\/|-]\d{1,2}[\.|\/|-]\d{4}$/;

    if (dateFormat.test(s)) {
        // Remove any leading zeros from date values
        s = s.replace(/0*(\d*)/gi,"$1");
        var dateArray = s.split(/[\.|\/|-]/);
        // Correct month value
        dateArray[1] = dateArray[1]-1;

        if(dateArray[2].length != 4){
          return false;
        }

        var testDate = new Date(dateArray[2], dateArray[1], dateArray[0]);

        if (testDate.getDate()!=dateArray[0] || testDate.getMonth()!=dateArray[1] || testDate.getFullYear()!=dateArray[2]) {
            return false;
        } else {
            return true;
        }
    } else {
        return false;
    }
}

This adjustment will resolve the issue with the 0302 year problem but may not work for dates ending with a two-digit year like .14.

JavaScript has a flaw in its date validation that allows for incorrect dates like 'dd.mm.0302' or '27.08.0974' to pass through

Answer №1

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