Design Twitter

class Solution {
    constructor() {
        this.count=0;
        this.users = {};
        this.tweetMap={};
    }

    /**
     * @param {number} userId
     * @param {number} tweetId
     * @return {void}
     */
    postTweet(userId, tweetId) {
        const tweetList = this.tweetMap[userId] ? [...this.tweetMap[userId], [this.count,tweetId]] : [[this.count, tweetId]];
        if(tweetList.length > 10) tweetList.shift();
        this.tweetMap[userId] = tweetList;

        this.count--;
    }

    /**
     * @param {number} userId
     * @return {number[]}
     */
    getNewsFeed(userId) {
       const res = [];
       if(!this.users[userId])  this.users[userId] = new Set();
       this.users[userId] = this.users[userId].add(userId);
       const minHeap = new PriorityQueue((a,b) => a[0]-b[0]);

       if(this.users[userId].size >= 10){
        const maxHeap = new PriorityQueue((a, b) => b[0]-a[0]);
        for(const id of this.users[userId]){
            if(!this.tweetMap[id]) continue;
            const tweets = this.tweetMap[id];
            const idx = tweets.length - 1;
            const [cnt, tId] = tweets[idx];
            maxHeap.enqueue([cnt, tId, id, idx - 1]);
            if(maxHeap.size() > 10) maxHeap.dequeue();
        }
        while(maxHeap.size()){
            minHeap.enqueue(maxHeap.dequeue());
        }
       }else{
        for(const id of this.users[userId]){
            if(!this.tweetMap[id]) continue;
            const tweets = this.tweetMap[id];
            const idx = tweets.length - 1;
            const [cnt, tId] = tweets[idx];
            minHeap.enqueue([cnt, tId, id, idx - 1]);
        }
       }

       while(minHeap.size() > 0 && res.length < 10){
        const [_, tId, fId, idx] = minHeap.dequeue();
        res.push(tId);
         if (idx >= 0) {
            const [olderCount, olderTId] = this.tweetMap[fId][idx];
            minHeap.enqueue([olderCount, olderTId, fId, idx - 1]);
         }
       }

       return res;
    }

    /**
     * @param {number} followerId
     * @param {number} followeeId
     * @return {void}
     */
    follow(followerId, followeeId) {
        const setOfFollowers = this.users[followerId] ? this.users[followerId] : new Set();
        setOfFollowers.add(followeeId)
        this.users[followerId] = setOfFollowers;
    }

    /**
     * @param {number} followerId
     * @param {number} followeeId
     * @return {void}
     */
    unfollow(followerId, followeeId) {
        const setOfFollowers = this.users[followerId] ? this.users[followerId] : null;
        if(!setOfFollowers) return;
        
        setOfFollowers.delete(followeeId);
        this.users[followerId] = setOfFollowers;
    }
}