Automatic wc cart update when quantity change

/**
 * Auto update cart after quantity change
 *
 * @return  string
 **/
add_action( 'wp_footer', 'cart_auto_update_qty_script' );
function cart_auto_update_qty_script() {
    if ( is_cart() ) : ?>
      <script>
          jQuery('div.woocommerce').on('change', '.qty', function(){
              jQuery("[name='update_cart']").trigger("click"); 
          });
      </script>
    <?php endif;
}

// hide with CSS
.woocommerce-cart [name="update_cart"] {
  display: none;
}