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Q: Airport Statistics - JavaScript task

+1 vote

You started to work in company that outsources software. Recently the company was contracted to create a software for the new airport that is going be built in your town. Since you have just started, you received a simple task: create a program that generates statistics of the arrival/departure flights.

Write a JS program that aggregates information about airplane traffic to and from an airport. You will receive an array of strings in the following format:

{planeID} {town} {passengersCount} {action}

  • planeID – the ID of the plane
  • town – name of the town, which the plane is coming from, or the town the plane is going to
  • passerngersCount – the number of passengers on the plane (this element must be parsed as Number)
  • action – could be either "land" or "depart"

Store in your program the IDs of planes that land and remove them when they depart. If a plane is landing (indicated by  its  action),  then  the  passengers  on  it  are  arrivals  to  our  airport.  If  it’s  departing,  then  the  passengers  are departures. Some of the records will not be valid!

To be considered valid, a record must meet the following criteria:

  • A plane can depart only if it landed first.
  • A plane cannot land again if it’s already landed – it must depart between landings.
  • The same plane can land and depart multiple times (see the examples). If any of the above rules is not followed ignore that input string.

Your program should generate a report containing:

  • The IDs of planes that remain at our airport (their last valid action is land). Sort them alphabetically.
  • A list of towns with the number of arrivals  and departures  for each  town,  and all unique  IDs  of the planes that made the flights. Sort the towns by the number  of arrivals  (descending). If two towns have the same number, sort them alphabetically by name (ascending). Sort the list of planes for each town alphabetically.

See the examples for formatting details. Note the default behavior of Array.sort() in JavaScript will sort by ASCII code, which is not the same as alphabetical.

Data is passed to your program as an array of strings in the format described above.

Print on the console the aggregated data, sorted as described above, formatted as seen in the examples.


  • The input will always be in the specified formats. There is no need to check it explicitly.
  • Plane IDs can consist of any alphanumeric character

"Boeing474 Madrid 300 land",
"AirForceOne WashingtonDC 178 land",
"Airbus London 265 depart",
"ATR72 WashingtonDC 272 land",
"ATR72 Madrid 135 depart"

Planes left:
- AirForceOne
- Boeing474
Arrivals: 450
Departures: 0
-- AirForceOne
-- ATR72
Arrivals: 300
Departures: 135
-- ATR72
-- Boeing474

Boing474 landed with 300 passengers from Madrid. Later on, ART72 departed, flying to Madrid with 135 passengers.

From WashingtonDC there were two planes that landed with total of 450 passengers.

Airbus cannot depart, since it did not land beforehand.

"Airbus Paris 356 land",
"Airbus London 321 land",
"Airbus Paris 213 depart",
"Airbus Ljubljana 250 land"

Planes left:
- Airbus
Arrivals: 356
Departures: 213
-- Airbus
Arrivals: 250
Departures: 0
-- Airbus

Airbus landed two consecutive times – the second one is ignored. After it's departure it can land again.

asked in JavaScript category by user hues
edited by user golearnweb

1 Answer

+1 vote

Here is the solution:

function airportStatistics(input) {
    let landedAirplanes = new Set();
    let airPorts = new Map();

    for (let flightData of input) {
        let [planeID, town, passengersCount, action] = flightData.split(' ');

        if ((flightData.trim() === '') ||
            (action === "land" && landedAirplanes.has(planeID)) ||
            (action === "depart" && !landedAirplanes.has(planeID))) {

        if (!airPorts.has(town)) {
            airPorts.set(town, {arrivals: 0, departures: 0, planes: new Set()});

        if (action === "land") {
            airPorts.get(town).arrivals += Number(passengersCount);
        } else {
            airPorts.get(town).departures += Number(passengersCount);


    console.log("Planes left:");
    let sortedLeftPlanes = [...landedAirplanes.keys()].sort((a, b) => a.localeCompare(b));
    for (let plane of sortedLeftPlanes) {
        console.log('- ' + plane);

    let sortedTowns = [...airPorts.entries()].sort(sortTowns);
    for (let [town, stats] of sortedTowns) {
        console.log('Arrivals: ' + stats.arrivals);
        console.log('Departures: ' + stats.departures);
        let sortedPlanes = [...stats.planes].sort((a, b) => a.localeCompare(b));
        sortedPlanes.forEach(p => console.log('-- ' + p));

    function sortTowns(a, b) {
        let arrivalsA = a[1].arrivals;
        let arrivalsB = b[1].arrivals;

        let result = arrivalsB - arrivalsA;
        if (result === 0) {
            result = a[0].localeCompare(b[0]);

        return result;

// airportStatistics(
//     [
//         "Boeing474 Madrid 300 land",
//         "",
//         "AirForceOne WashingtonDC 178 land",
//         "Airbus London 265 depart",
//         "ATR72 WashingtonDC 272 land",
//         "ATR72 Madrid 135 depart",
//         "ATR72 Madrid 135 land"
//     ]
// );

// airportStatistics([
//     "Airbus Paris 356 land",
//     "Airbus London 321 land",
//     "Airbus Paris 213 depart",
//     "Airbus Ljubljana 250 land"
// ]);

    'RTA72 London -10 land',
    'RTA#72 Brussels -110 depart',
    'RTA7!2 Warshaw 350 land',
    'RTA72 Riga -201 depart',
    'rta72 riga -13 land',
    'rta Riga -200 depart',


answered by user icabe