How to add quantity to product archives in WooCommerce (and keep ajax). From blog post: http://christianvarga.com/how-to-add-quantity-to-product-archives-in-woocommerce-and-keep-ajax

application.js

$('.input-text.qty', 'ul.products').on('input', function() {
  $(this).closest('li').find('.add_to_cart_button').data('quantity', $(this).val());
});

functions.php

<?php

add_action( 'woocommerce_after_shop_loop_item', 'my_custom_quantity_field', 6 ); 

function my_custom_quantity_field() {
  global $product;

  if ( ! $product->is_sold_individually() )
    woocommerce_quantity_input( array(
      'min_value' => apply_filters( 'woocommerce_quantity_input_min', 1, $product ),
      'max_value' => apply_filters( 'woocommerce_quantity_input_max', $product->backorders_allowed() ? '' : $product->get_stock_quantity(), $product )
    ) );
}