if (document.domain.toLowerCase().indexOf("domainName") != -1)

if(window.location.href.match(/://(.[^/]+)/)[1].toLowerCase().indexOf("domainName") != -1)

if(window.location.hostname.toLowerCase().indexOf("domainName") != -1)

if(location.hostname == "mysite.com"){

}

if(location.hostname.match('mysite')){} // will return null if no match is found

function isEquals(myhost){
              var hostName = window.location.hostname.split('.');
              myhost = myhost.split(".");
              //handle stuff like site:.com or ..com
              for (var x in myhost)
                if (myhost[x] == "") myhost.splice(x,1);

          //j is where to start comparing in the hostname of the url in question
          var j = hostName.length - myhost.length;
          for(var i in myhost)
          {
              //if j is undefined or doesn't equal the hostname to match return false
              if (!hostName[j] || hostName[j].toLowerCase() != host[i].toLowerCase())
                  return false;
              j++;
          }
          return true;
      }

window.location.hostname == "stackoverflow.com"?

var domainParts = window.location.hostname.split(".");
domainParts[domainParts.length - 2] == "stackoverflow"