array.push to an array within an array

Question

I'm trying to push JSON data to an array within an array. The problematic difference to other examples of this I can find is that both arrays are being built by a loop which I believe is the reason for the error I'm receiving. TypeError: Cannot call method 'push' of undefined

Here's a somewhat minimal example of what I'm trying to achieve.

var json = {origin: data.origin.name, destination: data.destination.name, trips: []};

for (var i = 0; i < data.trips.length; i++) {
    var departure = data.trips[i].dep.time;
    var arrival   = data.trips[i].arr.time;

    json.trips.push({departure: departure, arrival: arrival, nodes: []});

    for (var j = 0; j < data.trips[i].legs.length; j++) {
        json.trips.nodes.push({test: 'test'});
    }
}

The output I'm trying to create should be looking like this.

{
    origin: origin,
    destination: destination,
    trips: [
        {
            departure: departure,
            arrival: arrival,
            nodes: [
                {test: test},
                {test: test},
                {test: test}
            ]
        },
        {
            departure: departure,
            arrival: arrival,
            nodes: [
                {test: test},
                {test: test},
                {test: test}
            ]
        }
    ]
}

The test nodes are nonsensical, sure, but shouldn't adding them in this way be possible?

you need to hold temporary instance of the trip object, push node objects into the node array in the temporary trip object, then push the temporary trip object into the trip array in the json object. — nickk_can
– nickk_can, Commented Aug 6, 2014 at 23:19

Matt Harrison · Accepted Answer · 2014-08-06 23:01:17Z

2

The line:

json.trips.nodes.push({test: 'test'});

should be:

json.trips[i].nodes.push({test: 'test'});

answered Aug 6, 2014 at 23:01

Matt Harrison

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2 Comments

Kilian Over a year ago

Ah, so a simple syntax error was the culprit behind the type error. At least fixes the error, but the problem persists in a slightly different form. Don't quite know if I should edit the question accordingly or not as it does go into a different direction. Thanks though :)

Matt Harrison Over a year ago

If it's another question, you should post another question.

Malk · Accepted Answer · 2014-08-06 23:02:19Z

0

json.trips.nodes is indeed undefined. I believe you want to add it to the new item in the trip loop?

var json = {origin: data.origin.name, destination: data.destination.name, trips: []};

for (var i = 0; i < data.trips.length; i++) {
    var newNode = {
       departure: data.trips[i].dep.time,
       arrival: data.trips[i].arr.time, 
       nodes: []
    };

    for (var j = 0; j < data.trips[i].legs.length; j++) {
        newNode.nodes.push({test: 'test'});
    }
    json.trips.push(newNode);
}

answered Aug 6, 2014 at 23:02

Malk

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1 Comment

Claudia Over a year ago

This is not very reusable, and it would be hard to adjust for future use.

nickk_can · Accepted Answer · 2014-08-06 23:24:10Z

0

var json = {origin: data.origin.name, destination: data.destination.name, trips: []};

for (var i = 0; i < data.trips.length; i++) {
    var departure = data.trips[i].dep.time;
    var arrival   = data.trips[i].arr.time;


    var trip = {departure: departure, arrival: arrival, nodes: []}


    for (var j = 0; j < data.trips[i].legs.length; j++) {
        trip.nodes.push({test: 'test'});
    }
    json.trips.push(trip);

}

answered Aug 6, 2014 at 23:24

nickk_can

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2 Comments

Kilian Over a year ago

Thanks for the example and especially the comment above. But for a reason unbeknownst to me the nodes aren't being created as they should be. This just results in nodes: [Object] for every trip. Any ideas?

nickk_can Over a year ago

My suspicion is the call to "json.trips.nodes" is trying to access the trips object instead of the array and creating a node member. It is treating the trips member as an object.

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