How to return a value using context.executeQueryAsync?

Question

How can I get this function to return the value? In all the examples I have seen, folks use an alert in the delegate functions, but I need to return the value instead. When I call the function, it fetches me my default string, which means the executeQueryAsync is not setting the variable.

What am I doing wrong?

var thisuser = SPGetSPcurrentUser();
alert(thisuser);
//-------------------------------------------------------------------
var SPGetSPcurrentUser = function(){
    var spuserid = "Error";
    var context = new SP.ClientContext.get_current();
    this.website = context.get_web();
    this.currentUser = website.get_currentUser();
    context.load(currentUser);
    context.executeQueryAsync(
        function(sender, args){ this.spuserid = currentUser.get_loginName();},
        function(sender, args){ this.spuserid = 'request failed ' + args.get_message() + '\n'+ args.get_stackTrace();}
    )
    return spuserid;
}

Answer 1

As the method executeQueryAsync indicates it is asynchronous.
You can actually force the XMLHttpRequest to be synchronous, although that is beside the point.

What you are looking for is a callback function, something like this:

var getSpCurrentUser = function(callback) {
  var ctx = SP.ClientContext.get_current();
  var user = ctx.get_web().get_currentUser();

  ctx.load(user);
  ctx.executeQueryAsync(function() {
    callback(null, user);
  }, function(a, b) {
    callback(new Error(b.get_message()));
  });
};

getSpCurrentUser(function(error, user) {
  if (error) {
    console.error(error);
    return;
  }
  console.log(user.get_title());
});

Answer 2

This is the closest I've found to returning a variable reference for the logged-on user.

Try it out it's simple to test: 1. In IE browse to your SharePoint site, open developer tools press (f12) 2. Open the Console press (ctl + 2) 3. Switch line-mode with your cursor in the "Console input" press (ctl + alt + m) 4. Paste all the following contents into the console then press (ctl + enter)

function iWannaDoSomethingWith(thisUser){
 if(thisUser === null){
  alert('failed to get user');
 }
 else{
  alert('User name:' + thisUser.get_title() 
  + '\n Login Name:' + thisUser.get_loginName());
 }
}
function necessaryEvilToWireItAllTogether(nameOfFuncWeReallyWantToCall){
 if (typeof(nameOfFuncWeReallyWantToCall)==="function")
 {
  var ctx = new SP.ClientContext.get_current();
  var oWeb = ctx.get_web();
  var currentUser = oWeb.get_currentUser();
  currentUser.retrieve();
  ctx.load(oWeb);
  ctx.executeQueryAsync(
   function(){
    // successful Async call
    nameOfFuncWeReallyWantToCall(currentUser);
   },
   function(){
    // failed Async call
    nameOfFuncWeReallyWantToCall(null);
   }
  );    
 }
}
ExecuteOrDelayUntilScriptLoaded(function(){necessaryEvilToWireItAllTogether(iWannaDoSomethingWith);}, "sp.js");