SimpleTwitter

function Twitter() {
    this.userMap = new Map()
};

Twitter.prototype.createUser = function(userId){
    let userObj = {}
    userObj.funs = []
    userObj.msgList = []
    this.userMap.set(userId,userObj)
}

Twitter.prototype.createTwitter = function(userId, tweetId){
    let msgObj = {}
    msgObj.author = userId
    msgObj.tweetId = tweetId
    msgObj.time = +new Date()
    return msgObj
}

Twitter.prototype.postTwitter = function(userId, tweetId) {
    if(this.userMap.has(userId)){
        let userObj = this.userMap.get(userId)
        let msgObj = this.createTwitter(userId, tweetId)
        userObj.msgList.unshift(msgObj)
        userObj.funs.map((item)=>{
            let funsObj = this.userMap.get(item)
            funsObj.msgList.unshift(msgObj)
            this.userMap.set(item,funsObj)
        })
    }else{
        this.createUser(userId)
        let msgObj = this.createTwitter(userId,tweetId)
        let userObj = this.userMap.get(userId)
        userObj.msgList.unshift(msgObj)
        this.userMap.set(userId,userObj)
    }
};

Twitter.prototype.getNewsFeed = function(userId) {
    let newsFeedIDArr = []
    if(this.userMap.has(userId)){
        let userObj = this.userMap.get(userId)
        let newsFeedArr = userObj.msgList.length > 10 ?  userObj.msgList.slice(0,10) :  userObj.msgList
        newsFeedIDArr =  newsFeedArr.map((item)=> {
            return item.tweetId
        })
    }
    return newsFeedIDArr
};

Twitter.prototype.follow = function(followerId, followeeId) {
    if(!this.userMap.has(followerId)){
        this.createUser(followerId)
    }
    if(!this.userMap.has(followeeId)){
        this.createUser(followeeId)
    }
    let followerIdMsgList = this.userMap.get(followerId).msgList
    let followeeIdMsgList = this.userMap.get(followeeId).msgList
    followerIdMsgList = followerIdMsgList.concat(followeeIdMsgList)
    followerIdMsgList.sort((a,b)=>b.time-a.time)
    let followerIdObj = this.userMap.get(followerId)
    followerIdObj.msgList = followerIdMsgList
    this.userMap.set(followerId,followerIdObj)

    let userObj  = this.userMap.get(followeeId)
    userObj.funs.push(followerId)
    this.userMap.set(followeeId,userObj)
};

Twitter.prototype.unfollow = function(followerId, followeeId) {
    let followeeIdObj  = this.userMap.get(followeeId)
    followeeIdObj.funs = followeeIdObj.funs.filter((item)=>{
        return  item != followerId
    })
    this.userMap.set(followeeId,followeeIdObj)

    let followerIdObj = this.userMap.get(followerId)
    let msgList = []
    for(let i = 0;i < followerIdObj.msgList.length;i++){
        let item = followerIdObj.msgList[i]
        if(item.author != followeeId){
            msgList.push(item)
        }
    }
    followerIdObj.msgList = msgList
    this.userMap.set(followerId,followerIdObj)
};