How to Add a Free Gift with Purchase on Shopify?

				
					{% if cart.total_price >= 10000 %}
  {% assign free_gift_variant_id = 12345678 %}
  {% assign has_free_gift = false %}
  
  {% for item in cart.items %}
    {% if item.variant.id == free_gift_variant_id %}
      {% assign has_free_gift = true %}
      {% break %}
    {% endif %}
  {% endfor %}

  {% unless has_free_gift %}
    <script>
      fetch('/cart/add.js', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json'
        },
        body: JSON.stringify({
          items: [{
            quantity: 1,
            id: {{ free_gift_variant_id }}
          }]
        })
      })
      .then(response => location.reload());
    </script>
  {% endunless %}
{% endif %}