var spConfig = new Product.Config(<?php echo $_jsonConfig ?>);

//we create new function
    spConfig.setInitialState = function (dropdown_id)
    {
        //select dropdown
        var dropdown = $(dropdown_id);
        //remove empty option from dropdown so it is not selectable after initial selection
        // dropdown[0].remove();
        //alert(dropdown.length);
        if (dropdown.length == 2) {
            dropdown[0].remove();// for the removing choose an option
           }
        //change selections in dropdowns
        for (index = 0; index < dropdown.length; index++)
        {
            if (dropdown[index].value != "")
            {
                dropdown.selectedIndex = index;
                var element = dropdown;
                var event = 'change';
                //fire events
                if (document.createEventObject)
                {
                    var evt = document.createEventObject();
                    return element.fireEvent('on' + event, evt)
                } else
                {
                    var evt = document.createEvent("HTMLEvents");
                    evt.initEvent(event, true, true);
                    return !element.dispatchEvent(evt);
                }
            }
        }
    };
<?php foreach ($_attributes as $_attribute): ?>
        spConfig.setInitialState("attribute<?php echo $_attribute->getAttributeId() ?>")
<?php endforeach; ?>

<script>
/* Andrew Davie 100118
Where there is only one option left in the dropdowns, autoselect it.
*/
require(['jquery'], function($){
    $('select[id^="attribute"]').change(function(){
        var picked = this;
        setTimeout(function() {
                autoselect(picked);  //do the autoselect after everything else.
        }, 0);

    });
    function autoselect(picked){
        var nextsel = $(picked).parent().parent().next().find('select[id^="attribute"]');
        if($(nextsel).children().length==2){
            $(nextsel).find(':nth-child(2)', picked).prop('selected',true);
            $(nextsel).change();
        };
    };
});
</script>
<?= $block->getChildHtml() ?>