Session storage not updated after product is added to cart

I have used this plugin and just noticed an issue which prevents fair execution of “wc_fragments_refreshed” event.

Basically in your wc-ajax-product-add-to-cart-public.js you have this code:

if ( typeof $supports_html5_storage !== 'undefined' && $supports_html5_storage && typeof wc_cart_fragments_params !== 'undefined' && wc_cart_fragments_params ) {
    sessionStorage.setItem( wc_cart_fragments_params.fragment_name, JSON.stringify( data.fragments ) );
    set_cart_hash( data.cart_hash );

    if ( data.cart_hash ) {
        set_cart_creation_timestamp();
    }
}

However $supports_html5_storage, set_cart_hash, set_cart_creation_timestamp are not defined elsewhere in the file.

My suggested fix is wrapping the entire event with DOMDocumentLoaded event and copy these missing variables, functions from original WooCommerce files:

/* global wc_prod_ajax_to_cart */
(function( $ ) {
	'use strict';

	$( document.body ).ready( function() {

		/* Storage Handling */
		var $supports_html5_storage = true,
			cart_hash_key           = wc_cart_fragments_params.cart_hash_key;

		try {
			$supports_html5_storage = ( 'sessionStorage' in window && window.sessionStorage !== null );
			window.sessionStorage.setItem( 'wc', 'test' );
			window.sessionStorage.removeItem( 'wc' );
			window.localStorage.setItem( 'wc', 'test' );
			window.localStorage.removeItem( 'wc' );
		} catch( err ) {
			$supports_html5_storage = false;
		}

		/* Cart session creation time to base expiration on */
		function set_cart_creation_timestamp() {
			if ( $supports_html5_storage ) {
				sessionStorage.setItem( 'wc_cart_created', ( new Date() ).getTime() );
			}
		}

		/** Set the cart hash in both session and local storage */
		function set_cart_hash( cart_hash ) {
			if ( $supports_html5_storage ) {
				localStorage.setItem( cart_hash_key, cart_hash );
				sessionStorage.setItem( cart_hash_key, cart_hash );
			}
		}

		/**
		 * All of the code for your public-facing JavaScript source
		 * should reside in this file.
		 *
		 * Note: It has been assumed you will write jQuery code here, so the
		 * $ function reference has been prepared for usage within the scope
		 * of this function.
		 *
		 * This enables you to define handlers, for when the DOM is ready:
		 *
		 * $(function() {
		 *
		 * });
		 *
		 * When the window is loaded:
		 *
		 * $( window ).load(function() {
		 *
		 * });
		 *
		 * ...and/or other possibilities.
		 *
		 * Ideally, it is not considered best practise to attach more than a
		 * single DOM-ready or window-load handler for a particular page.
		 * Although scripts in the WordPress core, Plugins and Themes may be
		 * practising this, we should strive to set a better example in our own work.
		 */
		$(document).on('submit', 'body.single-product form.cart', function(e){
			e.preventDefault();
			var $this = $(this);
			$( document.body ).trigger( 'adding_to_cart' );
			if( wc_prod_ajax_to_cart.enable_blockui === '1' ) {
				$this.block({
					message: null,
					overlayCSS: {
						background: '#fff',
						opacity: 0.6
					}
				});
			}
			$.ajax({
				method: 'POST',
				url: wc_prod_ajax_to_cart.ajax_url,
				data: $this.serialize(),
				success: function( data ) {

					if ( data && data.fragments ) {
						$.each( data.fragments, function( key, value ) {
							$( key ).replaceWith( value );
						});

						if( wc_prod_ajax_to_cart.enable_blockui === '1' ) {
							$this.unblock();
						}

						if ( typeof $supports_html5_storage !== 'undefined' && $supports_html5_storage && typeof wc_cart_fragments_params !== 'undefined' && wc_cart_fragments_params ) {
							sessionStorage.setItem( wc_cart_fragments_params.fragment_name, JSON.stringify( data.fragments ) );
							set_cart_hash( data.cart_hash );

							if ( data.cart_hash ) {
								set_cart_creation_timestamp();
							}
						}

						$( document.body ).trigger( 'wc_fragments_refreshed' );
					}
				},
				error: function( response ) {
					$( document.body ).trigger( 'added_to_cart' );
					if( wc_prod_ajax_to_cart.enable_blockui === '1' ) {
						$this.unblock();
					}
				},
			});
		});
	} );

})( jQuery );

Link to file:
https://d.pr/f/tiwwAn

I hope you can fix this issue.