server.js

var express = require('express'),
    bodyParser = require('body-parser'),
    ws = require('./ws'),
    WebSocket = require('ws'),
    Joi = require('joi'),
    expressJoi = require('express-joi-validator'),
    axios = require('axios'),
    mongoose = require('mongoose'),
    Model = require('./models'),
    { Stock } = Model,
    app = express();

app.use(bodyParser.json());

mongoose.connect("mongodb://akash:akash@ds121599.mlab.com:21599/stock")
  .then(
        ()=>{console.log('connected');},
        err =>{console.log('Error Connecting to DataBase');}
);

const schema = {
    query: {
        ticker: Joi.string().required(),
	dataType: Joi.string().default("Close"),
	startDate: Joi.string(),
	endDate: Joi.string(),
    }
};

var ws2 = new WebSocket('ws://localhost:40510');


app.get('/stock' ,expressJoi(schema), function (req, res, next) {
	var dt = req.query.dataType;
	var finalarr = [];
	Stock.findOne({ticker:req.query.ticker})
      	     .exec((err, products) => {
	if(products==null)
	{
		ws2.send(req.query.ticker);
		ws2.on('message', function (message) {
			var msg = JSON.parse(message);
			Stock.findOneAndUpdate({
				ticker:req.query.ticker},
				msg, {upsert: true, 'new': true}, function(err, res) {
					console.log(res);})
			       .then(function(response) {
				var sp=0,ep=response.priceHistory['Dates'].length-1;
				for(var i=0;i<response.priceHistory['Dates'].length;i++)
				{
					if(req.query.startDate)
					{	
						if(response.priceHistory['Dates'][i]==req.query.startDate)
							sp=i;
					}
					if(req.query.endDate)
					{
						if(response.priceHistory['Dates'][i]==req.query.startDate)
						{
							ep=i;
							break;
						}
				}
			}
			res.json(response.priceHistory[dt].slice(sp,ep+1));
			console.log('Done!');
			})
    	    	})
	}
	else
	{ 
		var sp=0,ep=products.priceHistory['Dates'].length-1;
  		for(var i=0;i<products.priceHistory['Dates'].length;i++)
  		{
    			if(req.query.startDate)
    			{	
				if(products.priceHistory['Dates'][i]==req.query.startDate)
      					sp=i;
    			}
    			
			if(req.query.endDate)
    			{
			    if(products.priceHistory['Dates'][i]==req.query.startDate)
			    {
			     	 ep=i;
			      	 break;
			     }
			}
		}
  		res.json(products.priceHistory[dt].slice(sp,ep+1));
	}
     })
});

app.use(function (err, req, res, next) {
    if (err.isBoom) {
         return res.status(err.output.statusCode).json(err.output.payload);
    }
});

app.listen(3000, function () {
  console.log('Example app listening on port 3000!')
});