Repopulating dates on select boxes

Question

I\'ve created a date_select in Rails (which is 3 select boxes: one for year, one for month, and one for day).

To have 31st February on them is quite confusing. What

Answer 1

I assume you have three selects with classes 'day', 'month', 'year'. Then use this JS:

function monthChanged() {
    var days = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
    var month = $('.month').val() - 1, year = +$('.year').val();
    var diff;

    // Check for leap year if Feb
    if (month == 1 && new Date(year, month, 29).getMonth() == 1) days[1]++;

    // Add/Remove options
    diff = $('.day option').length - (days[month] + 1);
    if (diff > 0) { // Remove
        $('.day option').slice(days[month] + 1).remove();
    } else if (diff < 0) { // Add
        for (var i = $('.day option').length; i <= days[month]; i++) {
            $('').attr('value', i).text(i).appendTo('.day');
        }
    }
}

$(function () {
    monthChanged(); // On document ready
    $('.month').change(monthChanged); // On month change
    $('.year').change(monthChanged); // On year change (for leap years)
});

Demo: http://jsfiddle.net/FxBpB/