Updates Quantity on Checkout Form

Checkout Quantity

function add_quantity( $product_title, $cart_item, $cart_item_key ) {

    /* Checkout page check */
    if (  is_checkout() ) {
        /* Get Cart of the user */
            $cart = WC()->cart->get_cart();
            foreach ( $cart as $cart_key => $cart_value ){
               if ( $cart_key == $cart_item_key ){
                    $product_id = $cart_item['product_id'];
                    $_product   = $cart_item['data'] ;

                    /* Add delete icon */
                    $return_value = sprintf(
                      '<a href="%s" class="remove" title="%s" data-product_id="%s" data-product_sku="%s">&times;</a>',
                      esc_url( WC()->cart->get_remove_url( $cart_key ) ),
                      __( 'Remove this item', 'woocommerce' ),
                      esc_attr( $product_id ),
                      esc_attr( $_product->get_sku() )
                    );

                    /* Add product name */
                    $return_value .= '<span class = "product_name" >' . $product_title . '</span>' ;

                    /* Add quantity selector */
                    if ( $_product->is_sold_individually() ) {
                      $return_value .= sprintf( '1 <input type="hidden" name="cart[%s][qty]" value="1" />', $cart_key );
                    } else {
                      $return_value .= woocommerce_quantity_input( array(
                          'input_name'  => "cart[{$cart_key}][qty]",
                          'input_value' => $cart_item['quantity'],
                          'max_value'   => $_product->backorders_allowed() ? '' : $_product->get_stock_quantity(),
                          'min_value'   => '1'
                          ), $_product, false );
                    }
                    return $return_value;
                }
            }
    }else{
        /*
         * This will return the product name on the cart page.
         * As the filter used on checkout and cart are same.
         */
        $_product   = $cart_item['data'] ;
        $product_permalink = $_product->is_visible() ? $_product->get_permalink( $cart_item ) : '';
        if ( ! $product_permalink ) {
            $return_value = $_product->get_title();
        } else {
            $return_value = sprintf( '<a href="%s">%s</a>', esc_url( $product_permalink ), $_product->get_title());
        }
        return $return_value;
    }
}

/* Adds js at the footer to update Cart via ajax */
function add_quanity_js(){
    if ( is_checkout() ) {
      wp_enqueue_script( 'checkout_script', get_stylesheet_directory_uri() . "/js/update-checkout.js", '', '', false );

      $localize_script = array(
        'ajax_url' => admin_url( 'admin-ajax.php' )
      );
      wp_localize_script( 'checkout_script', 'add_quantity', $localize_script );
    }
  }

  add_action( 'wp_footer', 'add_quanity_js', 10 );

  //This loads values from ajax call
  //This is also used in our script.js file for our ajax call
  function load_ajax() {
    if ( !is_user_logged_in() ){
        add_action( 'wp_ajax_nopriv_update_order_review', 'update_order_review' );
    } else{
        add_action( 'wp_ajax_update_order_review', 'update_order_review' );
    }
  }

  add_action( 'init', 'load_ajax' );

  //This updates Order Review
  function update_order_review() {
    $values = array();
    parse_str($_POST['post_data'], $values);
    $cart = $values['cart'];
    foreach ( $cart as $cart_key => $cart_value ){
        WC()->cart->set_quantity( $cart_key, $cart_value['qty'], false );
        WC()->cart->calculate_totals();
        woocommerce_cart_totals();
    }
    wp_die();
  }
  
  /* Javascript */
(function ($) {
    $(function () {
        var $checkout = $('form.woocommerce-checkout');       

        //Update Cart
        $checkout.on('click', '.minus-btn, .plus-btn', function (e) {
            var $qty = $(this).closest('.quantity').find('.qty');           

            var data = {
                //Make sure the action here is the same as our load_ajax function
                //This is found in our function.php file
                action: 'update_order_review',
                security: wc_checkout_params.update_order_review_nonce,
                post_data: $('form.checkout').serialize()
            };

            $.ajax({
                type: 'POST',
                url: add_quantity.ajax_url,
                data: data,

                success: function (data) {
                    $qty.trigger('update_checkout');
                }
            });
        });
    });
})(jQuery);