Unable to query restful api to output json object in nodejs

Question

I am building a restful API to fetch data from an external API (https://api.exchangeratesapi.io/latest). The fetch is successful. However, I want a situation where if you query like so "/api/rates?currency=EUR,GBP,USD", you will get

"rates": {
   "EUR": 0.0377244605,
   "GBP": 0.033795458,
   "USD": 0.044824204
}

And if there is no query parameter, all the rates will be returned. I tried using ternary operator to pull out the figures when a query parameter is present, but I get the error "TypeError: Cannot read property 'rates' of undefined"

Below is my app.js file

const express = require("express");
const request = require('request');
const apiCallFromRequest = require('./Requests')

const app = express();
const exchangeRouter = express.Router();
const port = process.env.PORT || 4001;

exchangeRouter.route(`/rates`)
  .get((req, res) => {
    const queryParameter = req.query;
    // console.log(queryParameter.currency)
    
    apiCallFromRequest.callApi(function(response) {
      let cur = queryParameter.currency

      res.json({
        results: {
          base: queryParameter.base ? queryParameter.base : response.base,
          date: response.date,
          rates: queryParameter.currency ? queryParameter.currency.response.rates : response.rates
        }
      })
      res.end();
    });
  });

app.use('/api', exchangeRouter);

app.get('/', (req, res) => {
  res.send('Welcome to my nodemon API')
});

app.listen(port, () => {
  console.log(`Running on port ${port}`);
})

And my Request.js file

const request = require('request');
 
const URL = `https://api.exchangeratesapi.io/latest`;

const callExternalApiUsingRequest = (callback) => {
    request(URL, { json: true }, (err, res, body) => {
    if (err) { 
        return callback(err);
     }
    //  console.log("body: ", body)
    return callback({
        base: body.base,
        date: body.date,
        rates: body.rates
    });
    });
}

module.exports.callApi = callExternalApiUsingRequest;

queryParameter.currency.rates returns undefined @Mike Malyi. I don't know why I'm blocked from commenting under your your comment. — Chinonso
– Chinonso, Commented Feb 9, 2021 at 22:01

khammami · Accepted Answer · 2021-02-11 12:19:35Z

1

As I can see you're trying to filter the response. It would be better to inject your query params into your external api call.

You're expecting currency as a query parameter /api/rates?currency=EUR,GBP,USD on your api. There is no response under currency that's why queryParameter.currency.rates is undefined

According to https://exchangeratesapi.io/ you can use symbols to achieve the same result:

GET https://api.exchangeratesapi.io/latest?symbols=USD,GBP HTTP/1.1

you may use the same query params as the external api for yours and use a function to inject them into the external call

answered Feb 11, 2021 at 12:19

khammami

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Comments

Chinonso · Accepted Answer · 2021-02-17 11:16:54Z

The solution. My app.js file should look like this:

const express = require("express");
const request = require('request');
const apiCallFromRequest = require('./Requests')

const app = express();
const exchangeRouter = express.Router();
const port = process.env.PORT || 4001;

exchangeRouter.route(`/rates`)
  .get((req, res) => {
    
    apiCallFromRequest.callApi(function(response) {
      if (!base && !currency) {
        return res.status(200).json({
          results: {
            "base": response.base,
            "date": response.date,
            "rates": response.rates
          }
        })
      }

      // If there is a query parameter but no value
      if (!base) {
        return res.status(400).json({ message: "Please specify your home currency" })
      }
      if (!currency) {
        return res.status(400).json({ message: "Please specify exchange currency or currencies" })
      }

      // If there is query parameter and a value
      const exchangeRates = currency.toUpperCase().split(',')
      let currencyExchangeRates = {};
      for (const exchangeRate of exchangeRates) {
        //trim white space
        const value = exchangeRate.trim();
        currencyExchangeRates = { ...currencyExchangeRates, [value]: response.rates[value] }
      }
      console.log(currencyExchangeRates);
      res.json({
        results: {
          "base": base,
          "date": response.date,
          "rates": currencyExchangeRates
        }
      })
      res.end();
    });
  });

app.use('/api', exchangeRouter);

app.get('/', (req, res) => {
  res.send('Welcome to my nodemon API')
});

app.listen(port, () => {
  console.log(`Running on port ${port}`);
})

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