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JavaScript

Tobias Graefe
Tobias Graefe
11,934 Points
Posted by Tobias Graefe
Tobias Graefe
11,934 Points

NodeJs modules and return values

I wrote a function that reads out all train stops in the city I live in from an API. I used the nodeJS https object. That works great. Now I want to transfer the data to my app.js file. I used "module.exports.getStopData = getStopData" and require in app.js. That works out great, but I don't get, how I can return data from my request.on("end") function.

stops.js

const https = require('https');

function getStopData(stopName){
    var request = https.get('https://data.webservice-kvb.koeln/service/opendata/haltestellen/json', response => {
        if(response.statusCode === 200){
            var body = "";
            response.on("data", data => {
                body += data.toString();
            });

            response.on("end", ()=>{
                let kvbData = JSON.parse(body).features;
                let stops = [];
                for(let stop in kvbData){
                    if(kvbData[stop].properties.Name === stopName){
                        stops.push(kvbData[stop]);
                    }
                } 
                return stops;
            });
        } 
    });

}


module.exports.getStopData = getStopData;

app.js

const stop = require('./stop');
const name = 'Heumarkt'

stop.getStopData(name);

Thanks everyone.

1 Answer

Alexandra Silcox
Alexandra Silcox
24,486 Points

You can do a couple things to return the data

1) Return stops in a callback function

stops.js

function getStopData(stopName, someCallBack){
     var request = https.get('https://data.webservice-kvb.koeln/service/opendata/haltestellen/json', response => {
        if(response.statusCode === 200){
            var body = "";
            response.on("data", data => {
                body += data.toString();
            });

            response.on("end", ()=>{
                let kvbData = JSON.parse(body).features;
                let stops = [];
                for(let stop in kvbData){
                    if(kvbData[stop].properties.Name === stopName){
                        stops.push(kvbData[stop]);
                    }
                } 
                someCallBack(stops);
            });
        } 
    });
}

app.js

const stop = require('./stops');
const name = 'Heumarkt'

stop.getStopData(name, () => console.log(res));

2. Return stops with a promise-based wrapper

stops.js

function getStopData(stopName){
   return new Promise(resolve => {
     var request = https.get('https://data.webservice-kvb.koeln/service/opendata/haltestellen/json', response => {
        if(response.statusCode === 200){
            var body = "";
            response.on("data", data => {
                body += data.toString();
            });

            response.on("end", ()=>{
                let kvbData = JSON.parse(body).features;
                let stops = [];
                for(let stop in kvbData){
                    if(kvbData[stop].properties.Name === stopName){
                        stops.push(kvbData[stop]);
                    }
                } 
                resolve(stops);
            });
        } 
    });
   });
}

app.js

const stop = require('./stops');
const name = 'Heumarkt'

stop.getStopData(name).then(res => {
console.log(res)
);

I hope this helps!