Version of Remy Sharps bookmarklet to check for globals, with the addition of ignoring global variables that are undefined and also alerting out a summary. If you want to add it to Chrome, there's a good guide here: http://crossbrowsertesting.com/faq/how-do-i-install-bookmarklet-google-chrome-mac-os

findglobals

javascript:(function(){var e={},t,n={},r=(prompt("Ignore filter (comma sep)?","")||"").split(","),i=r.length,s=document.createElement("iframe"),o="";while(i--){n[r[i]]=1}for(i in window){if(window[i]!==undefined){e[i]={type:typeof window[i],val:window[i]}}}s.style.display="none";document.body.appendChild(s);s.src="about:blank";s=s.contentWindow||s.contentDocument;for(i in e){if(typeof s[i]!="undefined")delete e[i];else if(n[e[i].type])delete e[i]}t="addEventListener,document,location,navigator,window".split(",");i=t.length;while(--i){delete e[t[i]]}var u=[];for(i in e){u.push(i)}alert(u.length?"Found these globals: "+u.join(", ")+". See details in the console!":"No globals found!");console.dir(e)})()