AccountManager.js

var MSG_FACTORY = {
    'INSUFFICIENT_BALANCE': 'You have not sufficient balance in your account',
    'WITHDRAW_LIMIT': 'Withdrawal amount is more than limit',
    'WITHDRAW': 'Money withdrawn from your account',
    'DEPOSIT': 'Money deposited to your account'
}

/* This module is to notify the user whenever there is an account balance related alert required, 
Its takes input and alert based on msg type */
function notifyUser(msg){
    switch(msg){
        case MSG_FACTORY.INSUFFICIENT_BALANCE: 
            return alert('You have not sufficient balance in your account');
        case MSG_FACTORY.WITHDRAW:
            return alert('You have withdrawn money from your account');
        case MSG_FACTORY.DEPOSIT:
            return alert('You have deposited money to your account');
    }
}

/* This module is to LOG the msg whenever there is an activity in the account. Like:- deposit or withdrawal */
function logger(msg, amount){
    switch(msg){
        case MSG_FACTORY.WITHDRAW:
            console.log('You have withdrawn money from your account '+amount+ 'on Date: ', new Date());
            return;
        case MSG_FACTORY.DEPOSIT:
            console.log('You have deposited money to your account '+amount+ 'on Date: ', new Date());
            return;
    }
}

/* AccountManager class is responsible for only managing deposit or withdrawal of money from account, Also it notify and alert
user*/
class AccountManager{
    constructor(){
        this.amount = 0;
        this.withdrawLimit = 10000;    
    }
    deposit(depositAmount) {
        this.amount = this.amount + depositAmount;
        logger(MSG_FACTORY.DEPOSIT, depositAmount);
    }
    withdraw(withdrawalAmount) {
        if(withdrawalAmount > this.amount) {
            notifyUser(MSG_FACTORY.INSUFFICIENT_BALANCE);
        } else if(withdrawalAmount > this.withdrawLimit){
            notifyUser(MSG_FACTORY.WITHDRAW_LIMIT);
        } else {
            this.amount = this.amount - withdrawalAmount;
            logger(MSG_FACTORY.WITHDRAW, withdrawalAmount);
        } 
    }
}
var obj = new AccountManager();

obj.deposit(1000);
obj.withdraw(500);