Using array.push yields undefined

Question

I'm creating a polling app that should log the users ip, and which selection they voted for in addition to what the time was when they voted.

To do this I imagined creating an object for each 'vote' that included each of these as a property and then pushing that object into an array would suit my needs quite well.

Everything was running fine up until I tried to use push my object into my array. What I have currently says that that my array is undefined.

What exactly is happening? I tried using an index and setting votingArray[i] to the object, but that gave an undefined error as well.

Here is my code:

    //Vote for the pet passed into by user
function vote(pet, time){
    linkService.incrementCount(pet);
    trackVote(pet, time);

    res.render('vote', { 
    pet: pet
});
}

var votingArray = [];

function trackVote(pet, time) {

    var voteObject = {
        time: time,
        pet: pet,
        ip: req.ip
        };

console.log(voteObject);
    votingArray.push(voteObject);
    console.log(votingArray);

}

function showResults(){
res.render('results', { 
  votingArray: votingArray
    });
}

And here is the error in my console:

(Line 69 is 'votingArray.push(voteObject);')

Express started on http://localhost:8080; press Ctrl-C to terminate.
{ time: 1474584882143, pet: 'scout', ip: '::ffff:10.240.1.15' }
TypeError: Cannot read property 'push' of undefined
at trackVote (/home/ubuntu/workspace/Projects/projectTwo/app.js:69:14)
at vote (/home/ubuntu/workspace/Projects/projectTwo/app.js:51:6)
at /home/ubuntu/workspace/Projects/projectTwo/app.js:43:6
at Layer.handle [as handle_request] (/home/ubuntu/workspace/Projects/projectTwo/node_modules/express/lib/router/layer.js:95:5)
at next (/home/ubuntu/workspace/Projects/projectTwo/node_modules/express/lib/router/route.js:131:13)
at Route.dispatch (/home/ubuntu/workspace/Projects/projectTwo/node_modules/express/lib/router/route.js:112:3)
at Layer.handle [as handle_request] (/home/ubuntu/workspace/Projects/projectTwo/node_modules/express/lib/router/layer.js:95:5)
at /home/ubuntu/workspace/Projects/projectTwo/node_modules/express/lib/router/index.js:277:22
at param (/home/ubuntu/workspace/Projects/projectTwo/node_modules/express/lib/router/index.js:349:14)
at param (/home/ubuntu/workspace/Projects/projectTwo/node_modules/express/lib/router/index.js:365:14)

Edit:

Due to a lot of people suggesting that I've declared, but not instantiated the varriable 'votingArray' as an array, and that my snippets haven't included everything I've rewritten what I have to meet those comments and answers.

I'm still getting the same error about votingArray.push.

Here is my new code:

var votingArray = [];

//Vote for the pet passed into by user
function vote(pet, time){
    linkService.incrementCount(pet);

    var votingObject = 
    {
        ip: req.ip,
        pet: pet,
        timecode: time
    };

    votingArray.push(votingObject);

    res.render('vote', { 
    pet: pet
    });
}


function showResults(){
res.render('results', {
  votingArray: votingArray
    });
}

Yes, but why is it undefined? I've declared it, and defining if I don't push into the array and console.log it, I receive the same error. — Augie Luebbers
– Augie Luebbers, Commented Sep 22, 2016 at 23:03
try to initialize votingArray with initial value, like var votingArray = []; — Telman
– Telman, Commented Sep 22, 2016 at 23:04
You have declared it. And that's it. It does not magically become an array when you call .push on an undefined thing. — VLAZ
– VLAZ, Commented Sep 22, 2016 at 23:04
@AugieLuebbers. Please, do not edit your question like you did, because it disrupts the relation between your original question and my answer. Instead, place your edit as a new paragraph. If you still have the same error, you need to provide us more informations, because this is not enough to understand how your whole code works. — user6586783
– user6586783, Commented Sep 22, 2016 at 23:12

score 2 · Accepted Answer · 2016-09-22 23:07:00Z

2

Your variable votingArray is not initialized. If you want it to be an array, you must replace the line

var votingArray;

with

var votingArray = []; // Empty array instance

edited Sep 22, 2016 at 23:07

answered Sep 22, 2016 at 23:03

user6586783

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4 Comments

VLAZ Over a year ago

To make it behave like an array well, it will be an array.

Augie Luebbers Over a year ago

Declaring it as such yields the same error code. I've updated my question.

zerkms Over a year ago

Have you restarted the app after that?

Augie Luebbers Over a year ago

I have restarted the app and have revised my question once more.

httpNick · Accepted Answer · 2016-09-22 23:12:58Z

0

initialize your array or pass it into the function instead of having a floating var in your file. We also can't see the usage of where trackVote is called in your question, but this would be my suggestion.

var votingArray = [];

function trackVote(pet, time) {

    var voteObject = {
        time: time,
        pet: pet,
        ip: req.ip
        };

    console.log(voteObject);
    votingArray.push(voteObject);
    console.log(votingArray);

}

to

function trackVote(pet, time) {
    var votingArray = [];
    var voteObject = {
        time: time,
        pet: pet,
        ip: req.ip
        };

    console.log(voteObject);
    votingArray.push(voteObject);
    console.log(votingArray);

}

or

function trackVote(pet, time, votingArray) {

    var voteObject = {
        time: time,
        pet: pet,
        ip: req.ip
        };

    console.log(voteObject);
    votingArray.push(voteObject);
    console.log(votingArray);

}

answered Sep 22, 2016 at 23:12

httpNick

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3 Comments

Augie Luebbers Over a year ago

I've trimmed down my code quite a bit, but before that even following your method gave me the same error.

httpNick Over a year ago

Where are you calling trackVote?

Augie Luebbers Over a year ago

With my current code, I no longer need to. I just do what the function trackVote did in function vote.

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