update_cart_on_quantity_change.php

<?php
/*
   update cart on quantity field value change
*/

function wc_qty_change_update_cart(){?>
            
            <script>
            jQuery(".qty").blur(function(){      
                jQuery("[name='update_cart']").trigger("click"); 
            });
            </script>   
            <?php
            }            
            add_action("wp_footer","wc_qty_change_update_cart");