Accessing nested Javascript object with variables

Question

I am trying to find the sum of each channel to get the total energy for energy_ac. This is the mapping.

var mappings = [
{
  floor: 13,
  name: 1301,
  room_type: 'room',
  energy_ac: [
    {deviceId: 15062, channels: ['ct1']},
    {deviceId: 15063, channels: ['ct1', 'ct2', 'ct3']}
  ],
  energy_light: [
    {deviceId: 15062, channels: ['ct4']}
  ],
  energy_socket1: [
    {deviceId: 15062, channels: ['ct5']}
  ],
  energy_socket2: [
    {deviceId: 15062, channels: ['ct5']}
  ]
}  ];

This is the data:

data = { '15062':
   { _id: 550fea1b46758f1505dd70c7,
 deviceId: '15062',
 link: 'http://egauge15062.egaug.es/cgi-bin/egauge-show?S&s=0&n=6&C&Z=LST-8',
 timestamp: 1427106327,
 ct1: 34,
 ct2: 0,
 ct3: 7,
 ct4: 572,
 ct5: 527 },
  '15063':
   { _id: 550fea1b46758f1505dd70c8,
 deviceId: '15063',
 link: 'http://egauge15062.egaug.es/cgi-bin/egauge-show?S&s=0&n=6&C&Z=LST-8',
 timestamp: 1427106327,
 ct1: 34,
 ct2: 0,
 ct3: 7,
 ct4: 572,
 ct5: 527 },
  '15064':
{ _id: 550fea1b46758f1505dd70c9,
 deviceId: '15064',
 link: 'http://egauge15062.egaug.es/cgi-bin/egauge-show?S&s=0&n=6&C&Z=LST-8',
 timestamp: 1427106327,
 ct1: 34,
 ct2: 0,
 ct3: 7,
 ct4: 572,
 ct5: 527 },
  '15065':
   { _id: 550fea1b46758f1505dd70ca,
 deviceId: '15065',
 link: 'http://egauge15062.egaug.es/cgi-bin/egauge-show?S&s=0&n=6&C&Z=LST-8',
 timestamp: 1427106327,
 ct1: 34,
 ct2: 0,
 ct3: 7,
 ct4: 572,
 ct5: 527 } }

This is my code:

mappings.forEach(function(room) {
  var hash = {};
  hash.floor = room.floor;
  hash.name = room.name;
  hash.room_type = room.room_type;
  hash.energy_ac = 0;
  room.energy_ac.forEach(function(device) {
    device.channels.forEach(function(channel){
      hash.energy_ac += room[device][channel];
    });
  });

room[device][channel] is not working for me. I also tried room[device].channel . I am not sure how to get the value of channel. Any help would be appreciated.

Can you post a reproducible example?

thefourtheye
– thefourtheye

2015-03-24 03:08:12 +00:00
Commented Mar 24, 2015 at 3:08 — thefourtheye
– thefourtheye, Commented Mar 24, 2015 at 3:08
I posted my actual code, is that what you mean?

Kelvin
– Kelvin

2015-03-24 03:18:22 +00:00
Commented Mar 24, 2015 at 3:18 — Kelvin
– Kelvin, Commented Mar 24, 2015 at 3:18

firefoxuser_1 · Accepted Answer · 2015-03-24 03:28:35Z

1

Device is nested inside of energy_ac, so you can't access it directly from room. You need to do something like room.energy_ac[device].channels[channel]. This still isn't going to work though, because channel isn't the index of the array, it's the current item, which is the channel value. What you really need to do is just run hash.energy_ac += channel, since channel is the number you want to add anyway.

edited Mar 24, 2015 at 3:28

answered Mar 24, 2015 at 3:23

firefoxuser_1

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Comments

mbil · Accepted Answer · 2015-03-24 03:53:04Z

I think the chief problem here is that you're attempting to get the energy from the device object, when it's actually stored in the data object. The keys you need to index into the data object are stored in device.

Assuming you want the total energy_ac per room, what you need to do is:

for each room:
    set hash.energy_ac = 0
    for each device in room's energy_ac:
        for each channel in this device:
          add the energy of this device and channel to hash.energy_ac

So for the one room in mappings (1301), the energy_ac should be 75. Its energy_ac is comprised of device 15062: channel ct1 (34), plus device 15063: channels ct1 (34) + ct2 (0) + ct3 (7). 34 + 34 + 7 = 75.

Here's a JSFiddle with (what I think is) the implementation you intended.

Also, I was getting console errors due to the _id values not being strings.

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