Exams - Concerts

/* You are given a timetable for the upcoming rock concerts. It consists of bands, towns, dates and venues,
 separated by '|'. Your task is to write a JavaScript function that prints at the console a JSON string that holds
 the towns, venues for each town and list of bands for each venue (see the example below). */

"use strict";

function printToJSONstring(arr) {
    var i;
    var concertMap = {};
    for (i = 0; i < arr.length; i += 1) {
        var lineArray = arr[i].split('|').filter(Boolean);
        var town = lineArray[1].trim();
        var stadium = lineArray[3].trim();
        var band = lineArray[0].trim();

        if (!(town in concertMap)) {
            concertMap[town] = {};
        }

        if (!(stadium in concertMap[town])) {
            concertMap[town][stadium] = [];
        }

        if (concertMap[town][stadium].indexOf(band) == -1) {
            concertMap[town][stadium].push(band);
        }
    }

    var townKeys = Object.keys(concertMap).sort();
    var outputMap = {};
    for (i = 0; i < townKeys.length; i += 1) {
        outputMap[townKeys[i]] = {};
        if (concertMap.hasOwnProperty(townKeys[i])) {
            var stadiumKeys = Object.keys(concertMap[townKeys[i]]).sort();
            for (var j = 0; j < stadiumKeys.length; j += 1) {
                if (concertMap[townKeys[i]].hasOwnProperty(stadiumKeys[j])) {
                    outputMap[townKeys[i]][stadiumKeys[j]] = concertMap[townKeys[i]][stadiumKeys[j]].sort();
                }
            }
        }
    }

    console.log(JSON.stringify(outputMap));
}

printToJSONstring([
    'ZZ Top | London | 2-Aug-2014 | Wembley Stadium',
    'Iron Maiden | London | 28-Jul-2014 | Wembley Stadium',
    'Metallica | Sofia | 11-Aug-2014 | Lokomotiv Stadium',
    'Helloween | Sofia | 1-Nov-2014 | Vassil Levski Stadium',
    'Iron Maiden | Sofia | 20-June-2015 | Vassil Levski Stadium',
    'Helloween | Sofia | 30-July-2015 | Vassil Levski Stadium',
    'Iron Maiden | Sofia | 26-Sep-2014 | Lokomotiv Stadium',
    'Helloween | London | 28-Jul-2014 | Wembley Stadium',
    'Twisted Sister | London | 30-Sep-2014 | Wembley Stadium',
    'Metallica | London | 03-Oct-2014 | Olympic Stadium',
    'Iron Maiden | Sofia | 11-Apr-2016 | Lokomotiv Stadium',
    'Iron Maiden | Buenos Aires | 03-Mar-2014 | River Plate Stadium'
]);