SharePoint 2013 get current user using JavaScript

I found a much easier way, it doesn't even use SP.UserProfiles.js. I don't know if it applies to each one's particular case, but definitely worth sharing.

//assume we have a client context called context.
var web = context.get_web();
var user = web.get_currentUser(); //must load this to access info.
context.load(user);
context.executeQueryAsync(function(){
    alert("User is: " + user.get_title()); //there is also id, email, so this is pretty useful.
}, function(){alert(":(");});

Anyways, thanks to your answers, I got to mingle a bit with UserProfiles, even though it is not really necessary for my case.

Here is the code that worked for me:

<script src="/SiteAssets/jquery.SPServices-2013.02a.js" type="text/javascript"></script>
<script src="/SiteAssets/jquery.js" type="text/javascript"></script>

<script type="text/javascript">
  var userid= _spPageContextInfo.userId;
  var requestUri = _spPageContextInfo.webAbsoluteUrl + "/_api/web/getuserbyid(" + userid + ")";
  var requestHeaders = { "accept" : "application/json;odata=verbose" };
  $.ajax({
    url : requestUri,
    contentType : "application/json;odata=verbose",
    headers : requestHeaders,
    success : onSuccess,
    error : onError
  });

  function onSuccess(data, request){
    var loginName = data.d.Title;
    alert(loginName);
  }

  function onError(error) {
    alert("error");
  }
</script>