Write distance results

writeDistanceResults.js

case 'WRITE_DISTANCE_RESULTS':
            return locations.map((location) => {
                if (location.ID === action.ID) {
                    let distances = [action.distance].concat(location.distances);
                    distances = distances.slice(0, action.locationArrayMaxLength);
                    let distanceAverage = distances.reduce(function (sum, value) {
                        return sum + value;
                    }, 0) / distances.length;
                    return Object.assign({},
                        location,
                        {
                            distances,
                            distanceAverage
                        });
                }
                return location;
            })