solution number 1

let solution = (record) => {
  let answer = [];
  let userChat = [];

  for (let i = 0; i < record.length; i++) {
    let command = record[i].split(" ")[0];
    let userId = record[i].split(" ")[1];
    let nickName = record[i].split(" ")[2];
    let checkExistingUser = userChat
      .map((data, index) => (data.userId === userId ? index : ""))
      .filter(String);

    let newData = {
      command,
      userId,
      nickName,
    };

    switch (command) {
      case "Leave":
        userChat.push({
          ...userChat[checkExistingUser],
          command,
        });
        break;
      case "Enter":
      case "Change":
        if (checkExistingUser.length >= 0) {
          // replace the nickName & existing data
          checkExistingUser.map((existingIndex) => {
            userChat[existingIndex] = {
              ...userChat[existingIndex],
              nickName: newData.nickName,
            };
          });
        }
        userChat.push(newData);
        break;
    }
  }

  userChat.map((finalData) => {
    const { nickName, command } = finalData;
    if (command === "Enter") {
      answer.push(nickName + " came in.");
    }
    if (command === "Leave") {
      answer.push(nickName + " has left.");
    }
  });
  return answer;
};

let record = [
  "Enter uid1234 Muzi",
  "Enter uid4567 Prodo",
  "Leave uid1234",
  "Enter uid1234 Prodo",
  "Change uid4567 Ryan",
];

// answer:
// ["Prodo came in.", "Ryan came in.",
// "Prodo has left.", "Prodo came in."]

console.log(solution(record));