Programming Fundamentals - Roli The Coder

function solve(params) {
  params.pop();
  let events = {};

  for (let param of params) {
    let [id, eventName, ...participants] = param.split(" ");

    if (!eventName.includes("#")) {
      continue;
    }

    if (!events.hasOwnProperty(id)) {
      events[id] = {
        eventId: id,
        eventName: eventName,
        participants: []
      };
    }

    if (events[id].eventId === id && events[id].eventName === eventName) {
      participants.forEach(participant => {
        if (!events[id].participants.includes(participant)) {
          events[id].participants.push(participant);
        }
      });
    }
  }

  Object.entries(events)
    .sort((a, b) => b[1].participants.length - a[1].participants.length)
    .forEach(event => {
      console.log(
        `${event[1].eventName.slice(1)} - ${event[1].participants.length}`
      );
      event[1].participants
        .sort((a, b) => a.localeCompare(b))
        .forEach(participant => console.log(participant));
    });
}