Regex to validate date format dd/mm/yyyy

Question

I need to validate a date string for the format dd/mm/yyyy with a regular expresssion.

This regex validates dd/mm/yyyy, but not the invalid

Answer 1

For those who look at these and get completely confused, here is an excerpt from my script. Unfortunately, all it does is match valid numbers in a date time input, and 31st Feb will be marked as valid, but as so many have said, regex really isn't the best tool to do this test.

To match a date in the format 'yyyy-MM-dd hh:mm' (Or indeed in whatever order you please)

var dateerrors = false;
var yearReg = '(201[4-9]|202[0-9])';            ///< Allows a number between 2014 and 2029
var monthReg = '(0[1-9]|1[0-2])';               ///< Allows a number between 00 and 12
var dayReg = '(0[1-9]|1[0-9]|2[0-9]|3[0-1])';   ///< Allows a number between 00 and 31
var hourReg = '([0-1][0-9]|2[0-3])';            ///< Allows a number between 00 and 24
var minReg = '([0-5][0-9])';                    ///< Allows a number between 00 and 59
var reg = new RegExp('^' + yearReg + '-' + monthReg + '-' + dayReg + ' ' + hourReg + ':' + minReg + '$', 'g');
$('input').filter(function () {return this.id.match(/myhtml_element_with_id_\d+_datetime/);}).each(function (e) {
    if (e > 0) {
        // Don't test the first input. This will use the default
        var val = $(this).val();
        if (val && !val.trim().match(reg)) {
            dateerrors = true;
            return false;
        }
    }
});
if (dateerrors) {
    alert('You must enter a validate date in the format "yyyy-mm-dd HH:MM", e.g. 2019-12-31 19:30');
    return false;
}

The above script starts off by building a regex object. It then finds all of the inputs whose id's match a certain pattern and then loops through these. I don't test the first input I find (if (e > 0)).

A bit of explanation:

var reg = new RegExp('^' + yearReg + '-' + monthReg + '-' + dayReg + ' ' + hourReg + ':' + minReg + '$', 'g');

^ means start of match, whereas $ means end of match.

return this.id.match(/myhtml_element_with_id_\d+_datetime/);

\d+ means match a single or a contiguous sequence of integers, so myhtml_element_with_id_56_datetime and myhtml_element_with_id_2_datetime will match, but myhtml_element_with_id_5a_datetime will not