Using WebSocket data outside of onmessage event

Question

Hey so I've been playing around with JavaScript learning in my free time and had a quick question. I am using websockets to look at crypto prices as shown in the code below:

let ethws = new WebSocket('wss://stream.binance.com:9443/ws/ethusdt@trade');
let btcws = new WebSocket('wss://stream.binance.com:9443/ws/btcusdt@trade');
let ethstockPriceElement = document.getElementById('eth-stock-price')
let btcstockPriceElement = document.getElementById('btc-stock-price')
let ethlastPrice = null;
let btclastPrice = null;

ethws.onmessage = (event) => {
    let ethstockObject = JSON.parse(event.data)
    let ethprice = parseFloat(ethstockObject.p).toFixed(2)
    ethstockPriceElement.innerText = ethprice
    ethstockPriceElement.style.color = !ethlastPrice || ethlastPrice === ethprice ? 'black' : ethprice > ethlastPrice ? 'green' : 'red';
    ethlastPrice = ethprice
}
btcws.onmessage = (event) => {
    let btcstockObject = JSON.parse(event.data)
    let btcprice = parseFloat(btcstockObject.p).toFixed(2)
    btcstockPriceElement.innerText = btcprice
    btcstockPriceElement.style.color = !btclastPrice || btclastPrice === btcprice ? 'black' : btcprice > btclastPrice ? 'green' : 'red';
    btclastPrice = btcprice
}

I was wanting to use push the price into an "updating" variable outside of the event so I could do something like 2btc price 3eth price then btcprice + ethprice to get a total live updating price of 2btc and 3eth. However I am unable to use the data outside of the event. What would be the best way to achieve this?

You should be able to use it outside the event handler. Of course, you can only use it *after* the event has occurred, not immediately after assigning the handler. — Barmar, Sep 29 '21 at 14:56
`ethprice` is local to the function, I was talking about `ethlastpPrice`. — Barmar, Sep 29 '21 at 14:58
@Barmar so if i try and console.log(ethlastPrice) I get null which I assume is because that's what i originally set it. How can I get ethlastPrice to continuously update so it's constantly got the new live price? Thanks for your response btw! — Stan Daily, Sep 29 '21 at 15:01
Add a button that executes `console.log(ethlastPrice)` in its click listener. Click on the button after the `onmessage` function displays the price. — Barmar, Sep 29 '21 at 15:02
@Barmar could you point me in the direction of any kind of documentation for this. I'm new so not 100% sure what I'm looking for. — Stan Daily, Sep 29 '21 at 15:16

Using WebSocket data outside of onmessage event

0 Answers0