Add a button to Steam store pages to open the current page in the native Steam Client

open_in_steam.js

 // ==UserScript==
// @name         Open in Steam Client Button
// @include      http://store.steampowered.com/app/*
// @grant        none
// ==/UserScript==
/* jshint -W097 */
'use strict';

$J('.apphub_OtherSiteInfo').after('<div class="apphub_OtherSiteInfo">' +
                                    '<a class="btnv6_blue_hoverfade btn_medium" style="margin-right: 3px;" href="steam://advertise/' + window.location.href.split('app/')[1] +'">' +
                                      '<span>Open in Steam Client</span>' +
                                    '</a>' +
                                  '</div>');