concert.js

function concert(input) {
    let index = 0;
    let line = input[index];
    index++;
    let record = {};
    let totalTime = 0;

    while (line !== 'Start!') {
        let menu = line.split('; ');
        let command = menu[0];
        let bandName = menu[1];
        let time = Number(menu[2]);
        let info = {};
        let members = [];

        if (command === 'Add') {
            let members = menu.slice(2).join('').split(', ');
            for (let member of members) {
                if (!record.hasOwnProperty(bandName)) {
                    record[bandName] = info;
                    record[bandName].members = members;
                    record[bandName].time = 0;
                } else if (!record[bandName].members.includes(member)) {
                    record[bandName].members.push(member);
                }
            }
        } else if (command === 'Play') {
            if (!record.hasOwnProperty(bandName)) {
                record[bandName] = info;
                record[bandName].members = members;
                record[bandName].time = time;
                totalTime += time;
            } else {
                record[bandName].time += time;
                totalTime += time;
            }
        }

        line = input[index];
        index++;
    }
    console.log(`Total time: ${totalTime}`);
    for (let bandName in record) {
        console.log(`${bandName} -> ${record[bandName].time}`);
    }
    for (let bandName in record) {
        console.log(bandName);
        for (let member of record[bandName].members) {
            console.log(`=> ${member}`);
        }
        break;
    }
}

concert(["Play; The Beatles; 2584",
    "Add; The Beatles; John Lennon, George Harrison, Ringo Starr",
    "Add; The Beatles; Paul McCartney, George Harrison",
    "Add; The Rolling Stones; Brian Jones, Mick Jagger, Keith Richards",
    "Play; The Rolling Stones; 4239",
    "Start!"]);

console.log('---');

concert(["Add; The Beatles; John Lennon, Paul McCartney",
    "Add; The Beatles; Paul McCartney, George Harrison",
    "Add; The Beatles; George Harrison, Ringo Starr",
    "Play; The Beatles; 3698",
    "Play; The Beatles; 3828",
    "Start!"]);

console.log('---');

concert(["Add; The Beatles; John Lennon, Paul McCartney, George Harrison, Ringo Starr",
    "Play; The Beatles; 4569",
    "Play; The Beatles; 2456",
    "Play; Queen; 1250",
    "Add; Queen; Freddie Mercury, Brian May, Roger Taylor, John Deacon",
    "Play; Queen; 6215",
    "Start!"]);