XSS--UserAgent

UserAgent.js

/**
 * Created with JetBrains WebStorm.
 * User: jonbug
 * Date: 13-9-7
 * Time: 下午4:11
 * To change this template use File | Settings | File Templates.
 */
function getUserAgent(){
    if(window.ActiveXObject){
        if(document.documentElement && typeof document.documentElement.style.maxHeight!="undefined"){
            if(typeof document.adoptNode != "undefined"){

            }
        }
        return "msie";
    }

    else if (typeof  window.opera != "undefined"){
        return "opera";
    }

    else if(typeof window.netscape != "undefined"){
        if(typeof window.Iterator != "undefined"){
            if(typeof document.styleSheets != "undefined"){

            }
        }
        return "mozilla";
    }
    else if(typeof window.pageXOffset != "undefined"){
        try{
            if(typeof external.AddSearchProvider != "undefined"){
                return "chrome";
            }
        }catch (e){
            return "safari";
        }
    }
    else {
        return "unknown";
    }
}

alert(getUserAgent());