Does the message api alter json objects?

[PedanticAvenger]

I'm being challenged by trying to pass objects from the companion to the watch.  I am continually unable to directly reference components of the object on the watch side.

Building a JSON object in the following function: 

function buildGraphData(data) {
  // Take the data in, move a step at a time from most recent back.
  // look at timestamps to determine if a missed poll happened and make that graph point disappear.
  let obj = JSON.parse(data);
  let graphpointindex = 0;
  lastTimestamp = 0;
  var indexarray = [];

  // build the index
  for (var x in obj) {
     indexarray.push({ 'key': x, '_id': obj[x]['_id'] });
  }

  // sort the index
  indexarray.sort(function (a, b) { 
     var as = a['_id'], 
         bs = b['_id']; 

     return as == bs ? 0 : (as > bs ? 1 : -1); 
  }); 

  for (let index = 0; index < indexarray.length; index++) {
    if (graphpointindex <= 23) {
      while ((currentTimestamp - obj[indexarray[index]['key']].date) >= 300) {
        points[graphpointindex] = -10;
        currentTimestamp = currentTimestamp - 300;
        graphpointindex++;
      }
      points[graphpointindex] = obj[indexarray[index]['key']].sgv;
      graphpointindex++;
      if (obj[indexarray[index]['key']].date > lastTimestamp) {
        lastTimestamp = obj[indexarray[index]['key']].date;
        bgTrend = obj[indexarray[index]['key']].direction;
      }
    }
  }
//  console.log("GraphData:" + points);
  const messageContent = {"bgdata" : [
    {
      "graphData": points, 
      "lastPollTime": lastTimestamp, 
      "currentTrend": bgTrend
    }
  ]};
  console.log("CompanionData:" + messageContent);
  console.log("CompanionString:" + JSON.stringify(messageContent));
  if (messaging.peerSocket.readyState === messaging.peerSocket.OPEN) {
    messaging.peerSocket.send(messageContent);
  }
}

The last two log lines before the message is sent produces the following (which at first glance looks alright to me.

• CompanionData:[object Object]
• CompanionString:{"bgdata":[{"graphData":[98,88,115,136,152,163,185,207,225,235,249,252,252,253,253,250,246,244,235,233,229,222,215,210],"lastPollTime":1521062652363,"currentTrend":"FortyFiveDown"}]

Now, on the watch I have the the receiving end of the message

messaging.peerSocket.onmessage = function(evt) {

  if (evt.data.hasOwnProperty("settings")) {
    console.log("Triggered a settings update.");
    updateSettings(evt.data)
  } else if (evt.data.hasOwnProperty("bgdata")) {
    console.log("Triggered a data update. " + JSON.stringify(evt.data));
    const graphData = evt.data.bgdata;
    console.log("Is it a string?:" + graphData);
    console.log("Stringify:" + JSON.stringify(graphData));
    updategraph(evt.data.bgdata.graphData, evt.data.bgdata.currentTrend, evt.data.bgdata.lastPollTime);
  } else if (evt.hasOwnProperty("theme")) {
    console.log("Triggered a theme update.");
//This theme stuff needs a re-do, don't forget!
    applyTheme(evt.data.background, evt.data.foreground);
    let json_theme = {"backg": evt.data.background, "foreg": evt.data.foreground};
    fs.writeFileSync("theme.txt", json_theme, "json");
  }
}

And the messages are:

• Triggered a data update. {"bgdata":[{"graphData":[98,88,115,136,152,163,185,207,225,235,249,252,252,253,253,250,246,244,235,233,229,222,215,210],"lastPollTime":1521062652363,"currentTrend":"FortyFiveDown"}]}
• Is it a string?:[object Object]
• Stringify:[{"graphData":[98,88,115,136,152,163,185,207,225,235,249,252,252,253,253,250,246,244,235,233,229,222,215,210],"lastPollTime":1521062652363,"currentTrend":"FortyFiveDown"}]

This is as far as I can get, I cannot reference evt.data.bgdata.graphData, it is always undefined.  I am at the point where I think I'm missing something small/basic but I've modified how this is handled multiple times with the same outcomes.  Does passing using the message API alter the data in some way I need to account for?

[PedanticAvenger · Accepted solution]

Wasn't seeing the obvious in front of me.  Namely....

  const messageContent = {"bgdata" : [
    {
      "graphData": points, 
      "lastPollTime": lastTimestamp, 
      "currentTrend": bgTrend
    }
  ]};

Isn't the same as...

  const messageContent = {"bgdata" : {
      "graphData": points, 
      "lastPollTime": lastTimestamp, 
      "currentTrend": bgTrend
    }
  };

Making the value of bgdata an array reverted it to 0 indexed references and everything in my code fell apart. 

[JonFitbit]

You have an array, so you need to get the first element.

const graphData =  JSON.parse('{"bgdata":[{"graphData":[98,88,115,136,152,163,185,207,225,235,249,252,252,253,253,250,246,244,235,233,229,222,215,210],"lastPollTime":1521062652363,"currentTrend":"FortyFiveDown"}]}');

console.log(graphData.bgdata[0].graphData);
// [98, 88, 115, 136, 152, 163, 185, 207, 225, 235, 249, 252, 252, 253, 253, 250, 246, 244, 235, 233, 229, 222, 215, 210]