array.push to an array within an array

Question

array.push to an array within an array

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?

javascript
arrays
node.js

Answer 1

The line:

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

should be:

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

Answer 2

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);
}

Answer 3

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);

}