Adding multiple drop down options to product pages

From Spiffy Stores Knowledge Base

This tutorial details how to update an existing theme to use Spiffy Stores' new multiple option javascript helper. This javascript helper will build multiple select drop-down boxes for a given product, so that users can easily select a product variant by selecting different values for each product option. A callback mechanism allows designers to provide a callback action to enable/disable their 'add to cart' button and update and price field, etc.

While designers can create their own selector methods if they like, using the built-in javascript helper is an easy way to implement multiple select boxes as a way to select product variants and custom options.

Quick Overview of Steps

  1. Add the new "option_dropdowns.js" javascript helper to your Theme.liquid file
  2. Update your Product.liquid template to use <select> tag and use unique ids
  3. Define a callback
  4. Instantiate javascript with valid parameters

1. Update your theme.liquid file to include the option_dropdowns.js javascript

To use the Option Dropdowns javascript, your theme must include the following code in the header of the Theme.liquid file.

Insert the following into the head section 

{{ 'mootools.js' | global_asset_url | script_tag }}
{{ 'option_dropdowns.js' | global_asset_url | script_tag }}

for example… 

<head>
  <title>{{ shop.name }} — {{ page_title }}</title>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
  {{ header.author }}
  {{ header.copyright }}
  {{ header.description }}
  {{ header.keywords }}
  {{ 'stylesheet.css' | asset_url | stylesheet_tag }}

  {{ 'mootools.js' | global_asset_url | script_tag }}
  {{ 'option_dropdowns.js' | global_asset_url | script_tag }}

  {{ content_for_header }}
</head>

2. Update your Product.liquid template

Inside your product.liquid file, ensure you have a <form> element that posts to the "/cart/add" action, and that contains a <select> element that contains all the variants for your given product.

For example: 

<form action="/cart/add" method="post">
  <select id="variant-select" name="id">
    {% for variant in product.variants %}
      {% if variant.available %}
        <option value="{{variant.id}}">{{ variant.title }} for {{ variant.price | money_with_currency }}{% if variant.price < variant.compare_at_price %} usually {{ variant.compare_at_price | money_with_currency }}{% endif %}</option>
      {% else %}
	<option value="{{variant.id}}" disabled="disabled">{{ variant.title }} - sold out!</option>
      {% endif %}
    {% endfor %}
  </select>

  <input name="cart-add" type="submit" class="button" id="cart-add" value="Buy Now!">
  <span id="price-field"></span>
</form>

You need to ensure the following elements are in place in your <form> to use Spiffy Stores' javascript helper:

  • use a <select> element as the selection method for your variants
  • the <select> element requires a unique id. ie: <select id='variant-select' name='id'>
  • there should be a div element with an id of "price-field" for messages when selecting different variants. This is used for updating the price of the product, or setting a 'unavailable' or 'sold out' message
  • the add to cart button should have an id of "cart-add". This is to allow the callback to enable/disable the button.

There are two components to the required javascript script:

  • Define a callback (which is called whenever a user changes one of the newly created <select> elements
  • Instantiate the javascript MultipleOptions model

3. Define a callback in your Product.liquid template

A callback is called whenever a user changes one of the new multiple <select> drop-down boxes. You can define a callback to perform whatever actions you need (for example, update the price, enable/disable the add to cart button if the particular option is not valid, etc.)

The format of the callback is: 

var selectCallback = function(variant, selector, price, compare_at_price) {
  <your code goes here>
}

This callback will be called when any of the new <select> elements is changed by a user. Your callback should handle the following cases:

  • When variant passed in is null (no valid variant with the selected options was found)
  • When variant passed in is not available (there is a variant with the selected options, but available = false)
  • When variant passed in is available



Here's a sample callback function for mootools: 

<script type="text/javascript">
<!--
  // mootools callback for multi variants dropdown selector
  var selectCallback = function(variant, selector, price, compare_at_price) {
    if (variant && variant.available == true) {
      // selected a valid variant
      $('cart-add').removeClass('disabled');    // remove unavailable class from add-to-cart button
      $('cart-add').disabled = false;           // re-enable add-to-cart button
      if (variant.price < variant.compare_at_price) {
        $('price-field').innerHTML = MultipleOptions.formatMoney(price, "{{shop.money_with_currency_format}}") + '<br/><small>Usually <span class="compare-at-price">' + MultipleOptions.formatMoney(compare_at_price, "{{shop.money_with_currency_format}}</span></small>"); // update price field
      } else {
        $('price-field').innerHTML = MultipleOptions.formatMoney(price, "{{shop.money_with_currency_format}}"); // update price field
      }
    } else {
      // variant doesn't exist
      $('cart-add').addClass('disabled');      // set add-to-cart button to unavailable class
      $('cart-add').disabled = true;           // disable add-to-cart button
      $('price-field').innerHTML = (variant) ? "Sold Out" : "Unavailable"; // update price-field message
    }
  };
-->
</script>

4. Instantiate MultipleOptions javascript

To use Spiffy Stores' javascript helper, you must instantiate MultipleOptions.Selectors with the id of the <select>, a javascript representation of the product, and a callback. This will hide the existing <select> element, build new <select> elements for each product option, and bind the callback to each selector. 

<script type="text/javascript">
<!--
  // initialize multi selector for product
  window.addEvent('domready', function() {
    new MultipleOptions.Selectors("variant-select", { product: {{ product | json }}, onVariantSelected: selectCallback });
  });
-->
</script>


Format of javascript is: 

   new MultipleOptions.Selectors(<domid of select>, { product: <product>, onVariantSelected: <callback>});


Here's a complete MooTools script that calls the Spiffy javascript helper to enabled multiple options for a product: 

<!--
  // mootools callback for multi variants dropdown selector
  var selectCallback = function(variant, selector, price, compare_at_price) {
    if (variant && variant.available == true) {
      // selected a valid variant
      $('cart-add').removeClass('disabled');    // remove unavailable class from add-to-cart button
      $('cart-add').disabled = false;           // reenable add-to-cart button
      if (variant.price < variant.compare_at_price) {
        $('price-field').innerHTML = MultipleOptions.formatMoney(price, "{{shop.money_with_currency_format}}") + '<br/><small>Usually <span class="compare-at-price">' + MultipleOptions.formatMoney(compare_at_price, "{{shop.money_with_currency_format}}</span></small>"); // update price field
      } else {
        $('price-field').innerHTML = MultipleOptions.formatMoney(price, "{{shop.money_with_currency_format}}"); // update price field
      }
    } else {
      // variant doesn't exist
      $('cart-add').addClass('disabled');      // set add-to-cart button to unavailable class
      $('cart-add').disabled = true;           // disable add-to-cart button
      $('price-field').innerHTML = (variant) ? "Sold Out" : "Unavailable"; // update price-field message
    }
  };

  // initialize multi selector for product
  window.addEvent('domready', function() {
    new MultipleOptions.Selectors("variant-select", { product: {{ product | json }}, onVariantSelected: selectCallback });
  });
-->
</script>

Use Liquid Snippets to include the JavaScript code

JavaScript code has been made available using Global Liquid Snippets, so it is not necessary to add the code directly to your template.

Please refer to the documentation on the snippet for your particular environment.

A full example using MooTools can be found here (it's a fake store"): http://fresh.spiffystores.com/products/apples

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