Construct new array of objects from object array

49659511.js

let response = [
  {
    title: "Map marker 1",
    lat: 10.0,
    lng: 10.0
  },
  {
    title: "Map marker 2",
    lat: 11.0,
    lng: 11.0
  },
  {
    title: 'Akward object'
  }
]

function markerToPosition(marker) {
  // you can do some asserts here
  // assert(typeof marker.title === 'string')
  // or handle errors
  if (!marker.hasOwnProperty('lat') && !marker.hasOwnProperty('lng')) {
    throw 'Invalid object'
  }

  return {
    position: {
      lat: marker.lat,
      lng: marker.lng
    }
  }
}

response.forEach(function (marker, i) {
  // you'll modify response instead of create another Array
  try {
    response[i] = markerToPosition(marker)
  } catch (e) {
    delete response[i]
  }
})

console.log(response)