JSFiddle - React, Tailwind, and code Playground

HTML

<div class="field_group">
<select name="items[0][item_type]" class="item_type">
     <option value="0">Bulding / Landscaping</option> 
     <option value="1">Full / Thin Veneer</option> 
</select>

<select class="select_custom" name="items[0][standard]">
      <option value="0">Standard</option> 
      <option value="1">Custom</option> 
</select>
</div>
<button id="more_fields">Add</button>

JavaScript

$('#more_fields').click(function(){
    $('.field_group:first').clone(true).hide().insertAfter('.field_group:last').slideDown('slow');
        var last = $('.field_group:last');
        var current =  $(".field_group").length - 1;
        //last.append(new_button.clone(true));
        last.find('select').val([]);
        last.find('select.item_type').attr("name", "items[" + current + "][item_type]");
        last.find('select.select_custom').attr("name", "items[" + current + "][standard]");
        last.find(".custom_products").css("display","none");
        last.find(".unit_selection").css("display","none");
        last.find(".landscape_selection").css("display","none");
        last.find(".veneer_selection").css("display","none");
        last.find(".comments_section").css("display","none");
        last.find(".standard").css('display','none');
    });