Cacher is the code snippet organizer for pro developers

{% comment %}
  To add a companion product to the cart automatically if a primary product is in cart:
  1. Create a new link list under your Navigation tab.
  2. In that link list, make the first link point to companion product.
  3. Copy your link list handle where indicated at line 9
  4. Set the minimum cart total required for the bonus product on line 10
{% endcomment %}

{% assign linklist = linklists['put-your-link-list-handle-here'] %}
{% assign min_total = 100 %}

{% comment %}
  You're done. Include this code in cart.liquid at the top or bottom.
{% endcomment %}

{% if linklist.links.size > 0 %}

  <script>!window.jQuery && document.write('<script src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"><\/script>')</script>
  
  <script>
  if (typeof Shopify === 'undefined') var Shopify = {};
	Shopify.cart = {{ cart | json }};
	Shopify.toAdd = {{ linklist.links.first.object.variants.first.id }};
	var pleaseAdd = false;
	var pleaseRemove = false;
	Shopify.idsInCart = [];
  
	for (var i=0; i<Shopify.cart.items.length; i++) {
	  Shopify.idsInCart.push(Shopify.cart.items[i].id);
	  if (Shopify.cart.items[i].id !== Shopify.toAdd) {
		if (Shopify.cart.total_price >= {{ min_total | times: 100 }}) {
	    	pleaseAdd = true;
		}
	  } else { // Bonus item is in cart
		if (Shopify.cart.total_price < {{ min_total | times: 100 }}) {
			pleaseRemove = true;	
		}
      }
	}

  if (pleaseAdd && (jQuery.inArray(Shopify.toAdd, Shopify.idsInCart) === -1)) {
    var params = {
      type: 'POST',
      url: '/cart/add.js',
      data: 'quantity=1&id=' + Shopify.toAdd,
      dataType: 'json',
      success: function(line_item) { 
        window.location.href = '/cart';
      }
    };
    jQuery.ajax(params);
  } else if (pleaseRemove) {
    var params = {
      type: 'POST',
      url: '/cart/update.js',
      data: 'updates[' + Shopify.toAdd + ']=0',
      dataType: 'json',
      success: function(line_item) { 
        window.location.href = '/cart';
      }
    };
    jQuery.ajax(params);
  }
  
  </script>

{% endif %}