title: Add Class to WooCommerce Add to Cart Button (only if it is not "Select Option" button)
body: <p>I'm trying to add a class to the WooCommerce Add to cart button. </p>
  
  <p>I'm able to make changes to the Add to cart button via <code>woocommerce/loop/add-to-cart.php</code></p>
  
  <p><strong>Here is what I changed my add-to-cart.php file to</strong></p>
  
  <pre><code>/**
   * Loop Add to Cart
   *
   * @author      WooThemes
   * @package     WooCommerce/Templates
    * @version     2.1.0
    */
  
   if ( ! defined( 'ABSPATH' ) ) {
       exit; // Exit if accessed directly
   }
  
   global $product;
  
   echo apply_filters( 'woocommerce_loop_add_to_cart_link',
       sprintf( '&lt;div class="add-to-cart-container"&gt;&lt;a href="%s" rel="nofollow" data-product_id="%s" data-product_sku="%s" data-quantity="%s" class="%s product_type_%s single_add_to_cart_button button alt ajax_add_to_cart"&gt;&lt;i class="fa fa-shopping-cart"&gt;&lt;/i&gt;&amp;nbsp; %s&lt;/a&gt;&lt;/div&gt;',
           esc_url( $product-&gt;add_to_cart_url() ),
           esc_attr( $product-&gt;id ),
           esc_attr( $product-&gt;get_sku() ),
           esc_attr( isset( $quantity ) ? $quantity : 1 ),
           $product-&gt;is_purchasable() &amp;&amp; $product-&gt;is_in_stock() ? 'add_to_cart_button' : '',
           esc_attr( $product-&gt;product_type ),
           esc_html( $product-&gt;add_to_cart_text() )
       ),
   $product );
  </code></pre>
  
  <p>I only want the <code>ajax_add_to_cart</code> class in the <code>&lt;a&gt;</code> applied to simple products, not the variable products that have a button with "Select options" text. but I'd like all other changes to be applied to both buttons.</p>
  
  <p>How can this be done?</p>