Error Handling

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

const verbose   = process.argv.includes ('--verbose');

//-----------------------------------------------------------------------------

const printSupportedExchanges = () => console.log ('Supported exchanges:', ccxt.exchanges.join (', '))

const printUsage = () => {
   console.log ('Usage: node', process.argv[1], 'id'.green)
   printSupportedExchanges ()
}

const run = async (id) => {

   // check if the exchange is supported by ccxt
   const exchangeFound = ccxt.exchanges.indexOf (id) > -1

   if (exchangeFound) {

       console.log ('Instantiating', id, 'exchange')

       // instantiate the exchange by id
       const exchange = new ccxt[id] ({ verbose })

       // try to load markets and catch the errors if any
       try {

           await exchange.loadMarkets ()

       } catch (e) {

           if (e instanceof ccxt.NetworkError) {
               console.log (exchange.id, 'loadMarkets failed due to a network error:', e.message)
           } else if (e instanceof ccxt.ExchangeError) {
               console.log (exchange.id, 'loadMarkets failed due to exchange error:', e.message)
           } else {
               console.log (exchange.id, 'loadMarkets failed with:', e.message)
           }

           // rethrow the error "higher up" the call chain
           throw e
       }

       // try to fetch a ticker and catch the errors if any
       try {

           const symbol = 'ETH/BTC'
           const response = await exchange.fetchTicker (symbol)
           console.log (response)

       } catch (e) {

           if (e instanceof ccxt.NetworkError) {
               console.log (exchange.id, 'fetchTicker failed due to a network error:', e.message)
           } else if (e instanceof ccxt.ExchangeError) {
               console.log (exchange.id, 'fetchTicker failed due to exchange error:', e.message)
           } else {
               console.log (exchange.id, 'fetchTicker failed with:', e.message)
           }

           // rethrow the error "higher up" the call chain
           throw e
       }

   } else {

       console.log ('Exchange', id, 'not found')
       printSupportedExchanges ()
   }
}

;(async function main () {

   if (process.argv.length > 2) {

       let id = process.argv[2]
       await run (id)

   } else {

       printUsage ()
   }

   process.exit ()

}) ()