jQuery(document).ready(function ($) {
    $('#add_field').on('click', function () {
        $('#event_span').show();
        var num = $('.clonedInput').length; // how many "duplicatable" input fields we currently have
        var newNum = new Number(num + 1);      // the numeric ID of the new input field being added
        // create the new element via clone(), and manipulate it's ID using newNum value
        var newElem = $('#event' + num).clone().attr('id', 'event' + newNum);
        // insert the new element after the last "duplicatable" input field
        $('#event' + num).after(newElem);
        // enable the "remove" button
        $('#del_field').removeAttr('disabled');
        // business rule: you can only add 10 occurrences
        if ( newNum == 20 ) {
            $('#add_field').attr('disabled', 'disabled');
		}
    });

    $('#del_field').on('click', function () {
        var num = $('.clonedInput').length; // how many "duplicatable" input fields we currently have
        $('#event' + num).remove();     // remove the last element
        // enable the "add" button
        $('#add_field').removeAttr('disabled');
        // if only one element remains, disable the "remove" button
        if ( num - 1 == 1 ) {
            $('#del_field').attr('disabled', 'disabled');
		}
        $('#event_span').hide();
    });
    $('#del_field').attr('disabled', 'disabled');
    $('#event_span').hide();
});