Question

Html

 <select id="combo1" class="combo" data-index="1">
        <option></option>
        <option val="Opt1">Opt1</option>
        <option val="Opt2">Opt2</option>
        <option val="Opt3">Opt3</option>
    </select>

jQuery

$('body').on('change', '.combo', function() {
    var selectedValue = $(this).val();

if ($(this).find('option').size() > 2) {
    var newComboBox = $(this).clone();
    var thisComboBoxIndex = parseInt($(this).attr('data-index'), 10);
    var newComboBoxIndex = thisComboBoxIndex + 1;

    $('.parentCombo' + thisComboBoxIndex).remove();

    if (selectedValue !== '') {
        newComboBox.attr('data-index', newComboBoxIndex);
        newComboBox.attr('id', 'combo' + newComboBoxIndex);
        newComboBox.addClass('parentCombo' + thisComboBoxIndex);
        newComboBox.find('option[val="' + selectedValue + '"]').remove();
        $('body').append(newComboBox);
    }
}
});

Fiddle

This code is working and is creating a new combobox everytime the one before is filled.

How can I have a linebreak every two dropdown? like this:

And how can I force it to fill always an even number of comboboxes. Eg. If it is only 3 combobox filled, must alert error.

Answer 1

This assumes you put your select boxes in a container that only holds the select boxes and the br’s. (updated with validation)

$('body').on('change', '.combo', function() {
    var selectedValue = $(this).val();

    if ($(this).find('option').size() > 2) {
        var newComboBox = $(this).clone();
        var thisComboBoxIndex = parseInt($(this).attr('data-index'), 10);
        var newComboBoxIndex = thisComboBoxIndex + 1;

        $('.parentCombo' + thisComboBoxIndex).remove();

        if (selectedValue !== '') {
            newComboBox.attr('data-index', newComboBoxIndex);
            newComboBox.attr('id', 'combo' + newComboBoxIndex);
            newComboBox.addClass('parentCombo' + thisComboBoxIndex);
            newComboBox.find('option[val="' + selectedValue + '"]').remove();
            $('body').append(newComboBox);
        }
        $('body br').remove();
        $('body select:odd').after($('<br />'));
    } 

    validate();
});

function validate() {
    var count = $('body select[value!=""]').length;
    if (count > 0 && count % 2 == 0) 
        $('#ok').text('OK!');
    else
        $('#ok').text('Not an even number selected');
}

​

http://jsfiddle.net/P5nV8/4/