ws-library-advanced.js

import lodash from 'lodash';
import WebSocket from 'ws';
import { EventEmitter } from 'events';

const APIKEY = process.env.POLY_API_KEY || 'YOUR_API_KEY'


/*
	This example also uses the ws (https://github.com/websockets/ws) library to connect to a websocket, 
	adding reconnection logic, as well as an easier 
	way to process each type of messages. We can use the `subscribe`
	method at any time to subscribe to more channels..
 */


class Polygon extends EventEmitter {
	constructor( params ){
		super()
		console.log('Polygon class initialized..')
		this.ws = null
		this.subscriptions = []
		this.apiKey = params.apiKey
		this.connect()
	}
	subscribe( channels ){
		// Add to our list of subscriptions:
		this.subscriptions.push( channels )
		this.subscriptions = lodash.flatten( this.subscriptions )
		// If these are additional subscriptions, only send the new ones:
		if( this.connected ) this.sendSubscriptions( channels )
	}
	connect(){
		this.connected = false
		this.ws = new WebSocket('wss://socket.polygon.io/crypto')
		this.ws.on('open', this.onOpen.bind( this ))
		this.ws.on('close', this.onDisconnect.bind( this ))
		this.ws.on('disconnect', this.onDisconnect.bind( this ))
		this.ws.on('error', this.onError.bind( this ))
		this.ws.on('message', this.onMessage.bind( this ))
	}
	onOpen(){
		// Authenticate:
		this.ws.send(`{"action":"auth","params":"${APIKEY}"}`)
		this.connected = true
		// Subscribe to Crypto Trades and SIP:
		this.sendSubscriptions( this.subscriptions )
	}
	sendSubscriptions( subscriptions ){
		this.ws.send(`{"action":"subscribe","params":"${subscriptions.join(',')}"}`)
	}
	onDisconnect(){
		setTimeout( this.connect.bind( this ), 2000 )
	}
	onError( e ){
		console.log('Error:', e)
	}
	onMessage( data ){
		data = JSON.parse( data )
		data.forEach(( msg ) => {
			if( msg.ev === 'status' ){
				console.log('Status Update:', msg.message)
			}
			this.emit(msg.ev, msg)
		})
	}
}



// Use our Polygon Class:
const client = new Polygon({ apiKey: APIKEY })

// Subscribe to trades:
client.subscribe([ 'XT.*' ])

// Wait 5sec, then subscribe to SIP:
setTimeout(() => {
	client.subscribe(['XS.*'])
}, 5000)

// When we receive a crypto trade:
client.on('XT', ( trade ) => {
	console.log('Trade:', trade)
})

// When we receive a crypto quote:
client.on('XS', ( quote ) => {
	console.log('Quote:', quote)
})