Express endpoint to perform CryptoCompare request and Chatfuel response

cryptocompare-express-server.js

const express = require('express');
const app = express();
const requestPromise = require('request-promise');

// Call this from JSON API like this:
//
// https://myserver.com/crypto?fromCurrency=gbp&toCurrency=btc&amount=32.67
//
app.get('/crypto', (request, response) => {
    // NOTE: There is no error checking for amount existing and from/to currencies being valid symbols
    // Assumes a single to and from currency
    const { fromCurrency, toCurrency, amount } = request.query;

    // Need to convert amount to a number as it's a string
    const conversionAmount = Number(amount);

    // Symbols have to be uppercase
    const fromCurrencyUpperCase = fromCurrency.toUpperCase();
    const toCurrencyUpperCase = toCurrency.toUpperCase();

    const options = {
        uri: `https://min-api.cryptocompare.com/data/price?fsym=${fromCurrencyUpperCase}&tsyms=${toCurrencyUpperCase}`,
        json: true
    };

    return requestPromise(options)
        .then((cryptoResponse) => {
            // Can now get the toCurrency using the uppercase symbol as it will be a key in the response
            const conversionAmount = cryptoResponse[toCurrencyUpperCase];

            // Do the multiplication to determine how much in the new currency
            const maxDecimalPlaces = 8; // BTC allows 8 decimal places but you might want to change this
            const convertedAmount = Number(amount * conversionAmount).toFixed(maxDecimalPlaces);

            const outputString = `Converted ${amount} ${fromCurrency} to ${convertedAmount} ${toCurrency}`;

            return response.json({
                messages: [
                    { text: outputString }
                ]
            });
        });
});

const port = process.env.PORT || 8080;
app.listen(port, () => {
    console.log('Your app is listening on port ' + port);
});

package.json

{
  "//1": "Making sure you have request and request-promise in your package.json",

  "name": "my-glitch-app",
  "version": "0.0.1",
  "description": "What am I about?",
  "main": "server.js",
  "scripts": {
    "start": "node server.js"
  },
  "dependencies": {
    "express": "^4.16.2",
    "request": "^2.34",
    "request-promise": "^4.2.2"
  },
  "engines": {
    "node": "8.x"
  },
  "repository": {
    "url": "https://glitch.com/edit/#!/welcome-project"
  },
  "license": "MIT",
  "keywords": [
    "node",
    "glitch",
    "express"
  ]
}