Need to update CSV file from websocket stream with node js

Question

I have simple websocket API from api.bitfinex.com/ws that stream changes on BTC/USD market. I'm struggle how to make this to update simple csv file, so when receive new data from ws to update csv. I try to use fast-csv, but without success. Here is my node js code:

    const WebSocket = require('ws');
    const ws = new WebSocket("wss://api.bitfinex.com/ws");

    const fs = require('fs');

    ws.onopen = function(){
        ws.send(JSON.stringify({'event':'subscribe', 'channel':'ticker', 'pair':'btcusd'}))
    };

    ws.onmessage = function(msg){ 

        var response = JSON.parse(msg.data); 
        if (response[1] !="hb"){
            console.log("Bitfin " + response[7]); 
            //HERE I need to update existing CSV file,
            //for example 
            //BTC,xxxx
            //ETH,xxxx
            //two columns, and n rows..
        }   
    };

So, any idea how to stream into csv (BTCUSD in row 1 column 2; ETH in row 2 column 2 etc)

Alechko · Accepted Answer · 2018-02-07 17:29:59Z

3

Seems to me that you should be using a writeStream. Something like that:

  const fs = require('fs')
  let writeStream = fs.createWriteStream(fileName)

  ws.onmessage = function(msg){
      //... your code ...
      writeStream.write(msg)
  }

  writeStream.on('finish', () => {
    console.log(`Finished writing!`)
  })

answered Feb 7, 2018 at 17:29

Alechko

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