return variable within asynchron function in nodeJS

Question

I've a little problem with nodeJS and their asynchron functions. I need a function which does a GET request for getting some API data and then commits some data back into 2 variables to the function call for further use. But the problem is, that I can't use the response data outside the asynchron request function to return some data.

Is there any possibility to realize that? If not how can I do something like that?

var geoData = function(address){
    // Google API Key
    apikey = 'XXX';
    // google API URL for geocoding
    var urlText = 'https://maps.googleapis.com/maps/api/geocode/json?address='
                + encodeURIComponent(address)+'&key=' + apikey;
    request(urlText, function (error, response, body) {
        if (!error && response.statusCode == 200) 
        jsonGeo = JSON.parse(body);           
        console.log(jsonGeo.results[0].geometry.location);
    }
})
// Variable jsonGeo isn't declared here
latitude = jsonGeo.results[0].geometry.location.lat;
longitude = jsonGeo.results[0].geometry.location.lng;

return [latitude,longitude];    
};

Thanks so much and sorry for my bad english!

Why don't you just add "latitude = jsonGeo.results[0].geometry.location.lat; longitude = jsonGeo.results[0].geometry.location.lng;" into your request callback function ? — grll
– grll, Commented Jul 18, 2015 at 23:05
You cannot do that. Forget about return in continuation passing style; use a callback. — elclanrs
– elclanrs, Commented Jul 18, 2015 at 23:06
I've done this before, but it creates just undefined results at function call. — km65
– km65, Commented Jul 18, 2015 at 23:07
@elclanrs: Could you give me a little example for this way? Thanks — km65
– km65, Commented Jul 18, 2015 at 23:09
@km65 In any reason you can deasync you async function. For example, use github.com/abbr/deasync — stdob--
– stdob--, Commented Jul 18, 2015 at 23:43

abs · Accepted Answer · 2015-07-18 23:18:07Z

1

Instead of of returning something use a callback for geoData which will do the necessary task .

var geoData = function(address, callback){
    // Google API Key
    apikey = 'XXX';
    // google API URL for geocoding
    var urlText = 'https://maps.googleapis.com/maps/api/geocode/json?address='+encodeURIComponent(address)+'&key='+apikey;
    request(urlText, function (error, response, body) {
        if (!error && response.statusCode == 200) {
            jsonGeo = JSON.parse(body);           
            console.log(jsonGeo.results[0].geometry.location);
            latitude = jsonGeo.results[0].geometry.location.lat;
            longitude = jsonGeo.results[0].geometry.location.lng;
            callback([latitude,longitude]);
        }
    })    
};

use it like this

geoData('myaddress', function(arr){
    console.log(arr[0], arr[1]);
});

edited Jul 18, 2015 at 23:18

answered Jul 18, 2015 at 23:12

abs

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4 Comments

km65 Over a year ago

Thanks for your fast and helpful answer! That's the solution.

km65 Over a year ago

This async world is really a doom loop ;-) But this way it works! Thanks

Dirk Horsten Over a year ago

Indeed, instead of fighting the async nature of node.js, adapt, adopt and enjoy it!

km65 Over a year ago

@Dirk: I'll try it ;-)

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