Bookmarklet: Add Facebook app to a page

javascript:(function(){var e,t,o;if(e=(""+window.location).match(/^https:\/\/developers.facebook.com\/apps\/(\d+)\/settings\/?/)){t=e[1];o=document.querySelector("input[name=site_url]").value}else{o=window.prompt('Enter the URL of the client\'s website as entered in the app\'s "Site URL" field under "Website" platform settings');if(!o)return;if(!/^https?/i.test(o))o=o.replace(/^(\/+)?/,"http://");t=window.prompt("Enter the Facebook app's ID:");if(!t)return}window.location="https://www.facebook.com/dialog/pagetab?app_id="+t+"&next="+o})();