Hash-table-google-interview-question.js

var map = {
    tkt1: {
        departure: 'Los Angeles',
        arrival: 'San Francisco'
    },
    tkt2: {
        departure: 'San Francisco',
        arrival: 'New York'
    },
    tkt3: {
        departure: 'Moscow',
        arrival: 'Mali'
    },
    tkt4: {
        departure: 'Barcelona',
        arrival: 'Moscow'
    },
    tkt5: {
        departure: 'New York',
        arrival: 'Barcelona'
    }
};

findDepartureArrival = function(map) {
    var hashMap = {};

    for (var tkt in map) {
        var depart = map[tkt].departure;
        var arriv = map[tkt].arrival;

        if (!(depart in hashMap))
            hashMap[depart] = -1;
        else
            hashMap[depart] = hashMap[depart] - 1;

        if (!(arriv in hashMap))
            hashMap[arriv] = 1;
        else
            hashMap[arriv] = hashMap[arriv] + 1;
    }
    return hashMap;
}

console.log(findDepartureArrival(map));
/*Output 
{ 'Los Angeles': -1,
  'San Francisco': 0,
  'New York': 0,
  Moscow: 0,
  Mali: 1,
  Barcelona: 0 }*/

you are on a biz trip and travelling from one city to another. you have a stack of unsorted flight boarding passes. only departure city and destination city are on the boarding pass. how do you find the first departure city and your final destination city, write the solution in javascript.

What does "var = tkt" means? Does it function like an index?