Nodejs undefined variable

Question

I have an empty database and im getting TypeError: Cannot read property 'id' of undefined

Im not sure how to check for a undefined variable, or even if this check should be in the db model

Express route

    app.all("/", function(req, res){  
      if(!req.isAuthenticated()) req.user = null;    
      Bid.findHighestBids(function(err, bids){
        if(err) throw err;
        User.findHighestBidder(bids[0].id, bids[0].amount, function(err, highest){
          if(err) throw err;
          highest.amount = bids[0].amount;  
          res.render("home", {user: req.user, bids: req.bids, highest: highest}); 
        });      
      });
    });

Snippet from the models, (there is no data so its not returning anything, which is the problem)

    BidSchema.statics.findHighestBids = function(done){
      var Bids = this; 
      var num = 5;  
      this.find()
      .sort('-amount')
      .limit(num)
      .exec(function(err,bids){
        if(err) throw err;
        done(null, bids);
      });   
    }

    UserSchema.statics.findHighestBidder = function(id, amount, done){
      var User = this; 
      this.findOne({ 'facebook.id' : id }, function(err, highest){
        if(err) throw err;
        if(!id) return done(null, highest);
        done(null, highest);
      });  
    }

reduce your code to a minimal bit of code that still exhibits the problem (serious. Do this. Don't just look at it and assume you know how it'll behave in reduced form). In the process of doing so, you're almost guaranteed to discover what went wrong yourself. — Mike 'Pomax' Kamermans
– Mike 'Pomax' Kamermans, Commented Sep 3, 2013 at 1:13

JohnnyHK · Accepted Answer · 2013-09-03 01:50:04Z

3

You're not checking that bids contains any elements before accessing the first one. Since you say you have no data, that's likely your problem:

Bid.findHighestBids(function(err, bids){
  if(err) throw err;
  User.findHighestBidder(bids[0].id, bids[0].amount, function(err, highest){
  ...

bids[0] returns undefined, which has no id property, and thus the error.

So do something like this instead:

Bid.findHighestBids(function(err, bids){
  if (err) throw err;
  if (bids.length) {
    User.findHighestBidder(bids[0].id, bids[0].amount, function(err, highest){
      if(err) throw err;
      highest.amount = bids[0].amount;  
      res.render("home", {user: req.user, bids: req.bids, highest: highest}); 
    });      
  } else {
    res.render(... whatever you need for the no bids case ...);
  }

edited Sep 3, 2013 at 1:50

answered Sep 3, 2013 at 1:20

JohnnyHK

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2 Comments

slebetman Over a year ago

It would be more helpful if you were to provide the if(bids).. solution/hint as well.

JohnnyHK Over a year ago

@slebetman True enough...I added an example of the sort of thing to do to fix it.

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