Getting undefined when trying to get an average

Question

I display 5 datapoints in array, then 5 datapoints in array and finally got a globalArray with this 2 array.

So what I want is:

• if the majority of Average is equal to 200, display "up" into a array
• if the majority of Average is different to 200, display "down" into a array and take the first timestamp where average is different to 200.

I am trying to do something but I got an error :

cannot read property 'Average' of undefined.

Expected result: ['up','down'] [null,2019-01-15T08:26:00.000Z]

// ***** SCRIPT CONTINUE
getAllMetrics(regions).then(res => {
  console.log(res);
  /*
  [[{Timestamp: 2019-01-15T08:26:00.000Z, Average: 200},
  {Timestamp: 2019-01-15T08:32:00.000Z, Average: 200},
  {Timestamp: 2019-01-15T08:26:00.000, Average: 200},
  {Timestamp: 2019-01-15T08:29:00.000Z, Average: 200},
  {Timestamp: 2019-01-15T08:35:00.000Z, Average: 200}],
  [{Timestamp: 2019-01-15T08:26:00.000Z, Average: 400},
  {Timestamp: 2019-01-15T08:32:00.000Z, Average: 400},
  {Timestamp: 2019-01-15T08:26:00.000, Average: 400},
  {Timestamp: 2019-01-15T08:29:00.000Z, Average: 200},
  {Timestamp: 2019-01-15T08:35:00.000Z, Average: 200}]] */
  tabRES = [];
  //Loop regions
  var i = -1;
  TsTAB = [null, null, null];

  var a=-1;
  while( tabReg[++a] ){
    TsTAB.push( null );
  }
  while (res[++i]) {
    Avg = {
      up: 0,
      down: 0
    };
    Ts = "";
    RespARRAY = res[i];
    var j = -1;
    while (RespARRAY[++j]) {
      if (RespARRAY[j].Average == 200) {
        Avg.up++ // IF 200 -> UP
          //and push array TS
      } else {
        Avg.down++ // -> DOWN
          //Retrieve the last 
          Ts = Ts || RespARRAY[j].Timestamp;
      }
    }
    if (Avg.up > Avg.down) {
      tabRES.push('up');
    } else {
      tabRES.push('down');
      TsTAB[i] = TsTAB[i] || Ts;
    }
  }
  console.log(tabRES);
  console.log(TsTAB);
}).catch(err => {
  console.log(err);
});

Answer 1

The error is caused by while (RespARRAY[++j]) . The loop needs an end condition. Currently, it iterates through your five values and looks for a sixth, which doesn't exist. So RespARRAY[j] is undefined, and javascript can't find the "average" property of that undefined value.

You could begin the loop with

if(j > 4){ break; }

or, better,

if(j >= RespARRAY.length){ break; }

or you could use a for loop. (See www.w3schools.com/js/js_loop_for.asp )

Note that you'll find this same issue in your outer ( i ) loop.