Automatically add Free Gift in Cart

cart-addon.liquid

{% comment %}
  Replace the text below with the handle of your add-on product.
{% endcomment %}

{% assign product = all_products['PRODUCT-HANDLE'] %}
<!-- Replace Product Handle with the handle of your product -->

{% unless cart.item_count == 0 or product.empty %}

	{% if product.variants.size > 1 %}
      {% for variant in product.variants %}
		{% if variant.available != false %}
			{% assign variant_id = variant.id %}
			{% break %}
		{% endif %}	
      {% endfor %}
	{% else %}
		{% assign variant_id = product.variants.first.id %}
    {% endif %}

  <script>
  (function($) {

/* Replace Product id with the id of your product */
    $('.remove-1438100750406').click(function(){
    	setCookie('no-free-gift', false, 1);
    });
    
    if(getCookie('secondcase') == 'true'){
    var cartItems = {{ cart.items | json }},
        qtyInTheCart = 0,
        cartUpdates = {};

    for (var i=0; i<cartItems.length; i++) {
      if ( cartItems[i].id === {{ variant_id }} ) {
        qtyInTheCart = cartItems[i].quantity;
        break;
      }
    }

    if ( ( cartItems.length === 1 ) && ( qtyInTheCart > 0 ) ) {
      cartUpdates = { {{ variant_id }}: 0 }
    }
    else if ( ( cartItems.length >= 1 ) && ( qtyInTheCart !== 1 ) ) {
      cartUpdates = { {{ variant_id }}: 1 }
    }
    else {
      return;
    }

    var params = {
      type: 'POST',
      url: '/cart/update.js',
      data: { updates: cartUpdates },
      dataType: 'json',
      success: function(stuff) { 
        window.location.href = '/cart';
      }
    };

    $.ajax(params);
    }

  })(jQuery);
  </script>

{% endunless %}