accessing template params ejs express - node.js

Question

I'm creating fleet management application, I've set up for vehicles' makes and models and I've established one-to-many relationship in my database model.
I'm trying to present the vehicle make along with its models, however, it doesn't seem to work, below is the code from my routes file:
router.get("/new",function(req,res){
var selectedMake;
Make.find({},function(err,result){
if(err){
console.log("an error occured while fetching the data");
}else{
if(req.query.id){
Make.findById(req.query.id,function(err,foundMake){
console.log("found the query string");
selectedMake = foundMake;
console.log(selectedMake);
})
}
res.render("vehicles/newvehiclemake",{makes:result,selected: selectedMake});
}
})
});
and here is the code where i'm trying to access variable "selected" in my .ejs file
<div class="row">
<div class="col-md-9 col-md-offset-3">
<table class="table table-striped">
<tr>
<th>Available Models</th>
</tr>
<% if(selected) { %>
<% selected.models.forEach(function(model){ %>
<tr><td><%= model.name %></td></tr>
<% }) %>
<% }else { %>
<tr><td>No Models available for the selected Make</td></tr>
<% } %>
</table>
</div>
</div>
the branch where selected should be executed is never reached and always i get No Models available for the selected Make
any clues?

Answer 1

I think that is because your Make.findById method is a asynchronous call. So your callback function(err,foundMake) is called after the res.render
Move your render call into the callback function, then it should work.
if(req.query.id){
Make.findById(req.query.id,function(err,foundMake){
console.log("found the query string");
selectedMake = foundMake;
// after the findById call finished, now it has value.
console.log(selectedMake);
// res.render should be called at this moment.
res.render("vehicles/newvehiclemake",{makes:result,selected: selectedMake});
})
// you would see this line is called before the data is ready.
console.log(selectedMake);
}