GetUserNameIntoQueryString

function CustomExecuteFunction() {
	var self = this;
	self.context = new SP.ClientContext.get_current();
	self.web = context.get_web();
	self.currentUser = web.get_currentUser();
	context.load(self.currentUser);
	
	self.asyncSuccess = function(sender, args) {
		var user = this.currentUser;
		console.log('asyncSuccess', user);		
		loc = window.location.href;		
		check = loc.indexOf('CurrentUser');
		if(check <0)
		{
			// if not the redirect with appended query string
			window.location= loc + "?CurrentUser=" + user.get_title();
		}
	};
	
	self.asyncFailure = function(sender, args) {
		alert('Request failed. \nError: ' + args.get_message() + '\nStackTrace: ' + args.get_stackTrace());
	};
	
	// actually fires off the AJAX request
	// more info: http://msdn.microsoft.com/en-us/library/dn168907.aspx
	context.executeQueryAsync(
		Function.createDelegate(self,self.asyncSuccess), 
		Function.createDelegate(self,self.asyncSuccess)
	);
}

ExecuteOrDelayUntilScriptLoaded(CustomExecuteFunction,'sp.js');