app.js

// Required Packages
const fetch = require('node-fetch');
const fs = require('fs');

// Defining my API Key
const key = 'key';

// Defining myData array that will be filled with objects with the design shown above.
let pairs = [
  { base: 'AUD', compared: ['CAD', 'CHF', 'JPY', 'NZD', 'USD'] },
  { base: 'BGN', compared: ['RON'] },
  { base: 'CAD', compared: ['CHF', 'JPY'] },
  { base: 'CHF', compared: ['BGN', 'JPY', 'RON'] },
  {
    base: 'EUR',
    compared: [
      'AUD',
      'CAD',
      'CHF',
      'CZK',
      'DKK',
      'GBP',
      'HKD',
      'HUF',
      'ILS',
      'JPY',
      'NOK',
      'NZD',
      'PLN',
      'RON',
      'RUB',
      'SEK',
      'SGD',
      'TRY',
      'USD',
      'ZAR'
    ]
  },
  {
    base: 'GBP',
    compared: [
      'AUD',
      'BGN',
      'CAD',
      'CHF',
      'HKD',
      'JPY',
      'NZD',
      'PLN',
      'RON',
      'SGD',
      'USD',
      'ZAR'
    ]
  },
  { base: 'HKD', compared: ['JPY'] },
  { base: 'NZD', compared: ['CAD', 'CHF', 'JPY', 'USD'] },
  { base: 'SGD', compared: ['HKD', 'JPY'] },
  { base: 'TRY', compared: ['BGN', 'JPY', 'RON'] },
  {
    base: 'USD',
    compared: [
      'BGN',
      'CAD',
      'CHF',
      'CZK',
      'DKK',
      'HKD',
      'HUF',
      'GBP',
      'HKD',
      'HUF',
      'ILS',
      'JPY',
      'MXN',
      'NOK',
      'PLN',
      'RON',
      'RUB',
      'SEK',
      'SGD',
      'TRY',
      'ZAR'
    ]
  }
];
let baseCurrency;
let pairCurrency;
let url;

function cyclePairs(candleCount, granularity) {
  pairs.forEach(element => {
    baseCurrency = element.base;
    element.compared.forEach(pair => {
      pairCurrency = pair;
      //   console.log(`${baseCurrency}/${pairCurrency}`);

      getData(baseCurrency, pairCurrency, candleCount, granularity);
    });
  });
}
async function getData(base, pair, candleCount, granularity) {
  url = `https://api-fxpractice.oanda.com/v3/instruments/${base}_${pair}/candles?price=B&granularity=${granularity}&count=${candleCount}`;

  let header = {
    method: 'GET',
    headers: {
      'Content-Type': 'application/json',
      Authorization: `Bearer ${key}`,
      'Accept-Datetime-Format': 'RFC3339',
      'Accept-Encoding': 'gzip, deflate',
      Connection: 'Keep-Alive'
    }
  };
  try {
    let response = await fetch(url, header);
    let data = response.json().then(data => {
      writeData(data);
    });
  } catch (err) {
    console.log(`${base}_${pair}`);
  }

  //   console.log(data.candles.length);
}
function writeData(obj) {
  let instrument = obj.instrument;
  let granularity = obj.granularity;
  let candles = obj.candles[0].bid;
  let volume = obj.candles[0].volume;
  let time = obj.candles[0].time;

  let customObj = {
    instrument: instrument,
    time: time,
    granularity: granularity,
    volume: volume,
    candles: candles
  };

  let fileName = instrument;
  let pathToFile = `./instruments/${fileName}.json`;

  try {
    let rawData = fs.readFileSync(pathToFile);
    let myInstrument = JSON.parse(rawData);

    myInstrument.data.push(customObj);

    let allRecords = JSON.stringify(myInstrument, null, 2);

    fs.writeFileSync(pathToFile, allRecords);
  } catch (err) {
    console.log(customObj);
  }

  //   console.log(customObj);
}

// MAIN FUNCTION
function main() {
  cyclePairs('1', 'D');
  //   getData('USD', 'CAD', '1', 'D');
}

main();
// cyclePairs(10, 'M1');