For loop only shows last value in array

I’m trying to list out a set of values, that only show the new updated values in an array, but unfortunately it is only printing out the last value in the array. How do I show all the values and not only the last one?

When I console.log out the longLat[itemIndex] this is what I see. They should be in the same array

Collapsed:

Expanded:

My code –

let longLat = []

for (let index of this.overwatchTargets) {
  let coordsArr = [index["longitude"], index["latitude"], index["userName"], index["dateTimeCaptured"]]
  longLat.push(coordsArr)

  for (let itemIndex in longLat) {
    // Update location coords
    this.map.getSource('data-source').setData({
      "type": "FeatureCollection",
      "features": [{
        "type": "Feature",
        "properties": {
          'description': "Dispatcher: " + longLat[itemIndex][2] + "\n" + "\Lng/Lat\:" + longLat[itemIndex][0] + " / " + longLat[itemIndex][1] + "\n" + "\StartTime\: " + longLat[itemIndex][3]
        },
        "geometry": {
          "type": "Point",
          "coordinates": longLat[itemIndex] <--- This should show all elements in the array, but only shows the last one
        }
      }]
    });
  }
}

>Solution :

You are passing a single-element array several times instead of passing a single collection of coordinates.

Try creating a method of

indexToFeature(index) {
  const {longitude, latitude, userName, dateTimeCaptured} = index;
  return {
    "type": "Feature",
    "properties": {
      'description': "Dispatcher: " + userName + "\n" + "\Lng/Lat\:" + longitude + " / " + latitude + "\n" + "\StartTime\: " + dateTimeCaptured
    },
    "geometry": {
      "type": "Point",
      "coordinates": [longitude, latitude, userName, dateTimeCaptured]
    }
  };
}

Then your main body can simply be

this.map.getSource('data-source').setData({
    "type": "FeatureCollection",
    "features": this.overwatchTargets.map(indexToFeature)
});

to call setData once, converting the entire array of overwatchTargets into an array of features.