Load Markets To Files

import ccxt from '../../js/ccxt.js';
import path from 'path';
import fs from 'fs';

const enableRateLimit = true,
     // exchange defaults
     // ------------------------------------------------------------------------
     // path to your folder, for example '/myproject/markets' or 'C:/myproject/markets'
     options = { enableRateLimit },
     // writes to current working directory if left empty
     // ------------------------------------------------------------------------
     // use a reasonable value for maxConcurrency to avoid network congestion
     // a burst of requests in a short period of time will cause
     // excessive competition for networking resources within the application
     folder = '',
     maxConcurrency = 7;

async function main () {

   const allExchanges = ccxt.exchanges.map (id => {
           try {
               return new ccxt[id] (options)
           } catch (e) {
               console.log ('Failed to initialize', id, e.constructor.name)
           }
       }).filter (x => x)
       , allExchangesByIds = ccxt.indexBy (allExchanges, 'id')
       , exchangeIds = Object.keys (allExchangesByIds)

   const load = async () => {
       while (exchangeIds.length > 0) {
           const id = exchangeIds.pop ()
           const exchange = allExchangesByIds[id]
           const file = path.join (folder, `saved-markets-${exchange.id}.json`)
           try {
               await exchange.loadMarkets ()
               const { id, markets } = exchange
               await writeFile (file, JSON.stringify ({ id, markets }))
               console.log ('Loaded markets from', id, 'to', file)
           } catch (e) {
               console.log ('Failed to load markets from', id, 'to', file, e.constructor.name)
           }
       }
   }

   const started = ccxt.milliseconds ()
   const loaders = Array (maxConcurrency).fill ().map (x => load ())
   await Promise.all (loaders)
   const stopped  = ccxt.milliseconds ()
   console.log ('Done loading', allExchanges.length, 'exchanges in', ((stopped - started) / 1000).toFixed (2), 'seconds')

   // other code...
}

main ()