如何正确导出从NodeJS中的API调用检索到的值

Question

I'm simply trying to get the latitude and longitude from a geolocation API so I can pass the data into another API call to get the weather. How do I make it so the values are assigned to the global variables? As of right now I'm getting undefined.

I've moved the variables in and out of the function. Tried to return the values within the function and export the function itself.

const https = require('https');

const locationApiKey = 
"KEY GOES HERE";

let lat;
let lon;
let cityState;

module.exports = location = https.get(`https://api.ipdata.co/?api-key=${locationApiKey}`, response => {
        try {
            let body = " ";

            response.on('data', data => {
                body += data.toString();
            });
            response.on('end', () => {
                const locationData = JSON.parse(body);
                // console.dir(locationData);
                lat = locationData.latitude;
                lon = locationData.longitude;
            });
        } catch (error) {
            console.error(error.message);
        }
    });

module.exports.lat = lat;
module.exports.lon = lon;

Answer 1

To export some value retrieved by an asynchronous call you need to wrap them in a Promise or a callback .

Using the promise style it will look like this

// File: api.js
module.exports = () => new Promise((resolve, reject) => {
  https.get(`https://api.ipdata.co/?api-key=${locationApiKey}`, response => {
    try {
      let body = " ";

      response.on('data', data => {
        body += data.toString();
      });
      response.on('end', () => {
        const { latitude, longitude } = JSON.parse(body);
        resolve({lat: latitude, lon: longitude});
      });
    } catch (error) {
      reject(error);
    }
  });
});

Then you can get the "wrapped" values like this

// File: caller.js
const getLocation = require('./api.js');

getLocation()
  .then(({lat, lon}) => {
    // The values are here

    console.log(`Latitude: ${lat}, Longitude: ${lon}`)
  }))
  .catch(console.error);