javascript regexp, validating date problem

Question

I have some code for validating date below:

function validateForm() {
var errFound = 0;       
//var patt_date = new RegExp(\"^((((19|20)(([02468][048])|([1         


        

Answer 1

Don't do the whole date validation with a regular expression, that's really pushing the limits of what regexps were designed for. I would suggest this procedure instead:

1. Check date against regexp /^\d{4}-\d{2}-\d{2}$/
2. Extract year, month, and day using substr() and convert to integers
3. Use some if statements to validate the integers. Like so:

    if (month == 2) {
        if (day == 29) {
            if (year % 4 != 0 || year % 100 == 0 && year % 400 != 0) {
                // fail
            }
        }
        else if (day > 28) {
            // fail
        }
    }
    else if (month == 4 || month == 6 || month  == 9 || month == 11) {
        if (day > 30) {
            // fail
        }
    }
    else {
        if (day > 31) {
            // fail
    }

(That could certainly be written more concisely) Alternatively, you could probably perform this validation using Javascript's Date class - you might have to do something like parsing the date, converting it back to a string, and checking if the two strings are equal. (I'm not a Javascript expert)