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// 1. Show Buttons
 
add_action( 'woocommerce_after_add_to_cart_quantity', 'bbloomer_display_quantity_plus' );
 
function bbloomer_display_quantity_plus() {
   echo '<button type="button" class="plus" >+</button>';
}
 
add_action( 'woocommerce_before_add_to_cart_quantity', 'bbloomer_display_quantity_minus' );
 
function bbloomer_display_quantity_minus() {
   echo '<button type="button" class="minus" >-</button>';
}
 
// -------------
// 2. Trigger jQuery script
 
add_action( 'wp_footer', 'bbloomer_add_cart_quantity_plus_minus' );
 
function bbloomer_add_cart_quantity_plus_minus() {
   // Only run this on the single product page
   if ( ! is_product() ) return;
   ?>
      <script type="text/javascript">
          
      jQuery(document).ready(function($){   
          
         $('form.cart').on( 'click', 'button.plus, button.minus', function() {
 
            // Get current quantity values
            var qty = $( this ).closest( 'form.cart' ).find( '.qty' );
            var val   = parseFloat(qty.val());
            var max = parseFloat(qty.attr( 'max' ));
            var min = parseFloat(qty.attr( 'min' ));
            var step = parseFloat(qty.attr( 'step' ));
 
            // Change the value if plus or minus
            if ( $( this ).is( '.plus' ) ) {
               if ( max && ( max <= val ) ) {
                  qty.val( max );
               } else {
                  qty.val( val + step );
               }
            } else {
               if ( min && ( min >= val ) ) {
                  qty.val( min );
               } else if ( val > 1 ) {
                  qty.val( val - step );
               }
            }
             
         });
          
      });
          
      </script>
   <?php
}


?>