title: Node.js - mongoose promises - loop through
body: <p>I am having a trouble with mongoose used with node.js. In my model I am having only group supervisor's ID, and in this route I want also to add supervisorName to variable (this name is stored in Group model). So, yeah, I've read some about promises, but still, I dont have any idea how to solve that. (Basically, I just want to loop through all groups, get their models from mongodb, and assign supervisor name to every group)</p>
  
  <pre><code>router.get('/manage', function(req, res, next) {
  Group.find({}, function(err, groups) {
      groups.forEach(function(group) {
          Group.findById(group.supervisor, function(err, supervisor) {
              group.supervisorName = supervisor.name;
              console.log(supervisor.name);
          });
      });
  }).then(function() {
      res.render('groups/groups_manage', {groups : groups});
  });
  });
  </code></pre>