Returning undefined value - Node.js

Question

I have the below function which correctly takes from the response the prefix and the suffix of the image and makes a variable result,which holds the url of the venue image. However when i return the result, i keep having undefined.What is going wrong here?

function getPhotoUrl(venue_id,venue_location,venue_query){
  request({
      url: 'https://api.foursquare.com/v2/venues/'+venue_id+'/photos',
      json:true,
      method: 'GET',
      qs: {
        client_id: 'my_id',
        client_secret: 'my_secret',
        near:venue_location,
        query: venue_query,
        v: '20171114',
        limit: 1
      }
    }, function(err, res, body) {
        var result="";
        if (err) {
          console.error(err);
        } else {
          console.log(body.response.photos.items[0].prefix+"300x500"+body.response.photos.items[0].suffix);      
      }
      result=body.response.photos.items[0].prefix+"300x500"+body.response.photos.items[0].suffix;
      return result; 
    }
  );
}

<!-- begin snippet: js hide: false console: true babel: false -->

The A in Ajax is meaningful, search SO for how to deal with the results of an async call. — Dave Newton, Nov 14 '17 at 15:47
You cannot [return from a callback](https://stackoverflow.com/questions/23339907/returning-a-value-from-callback-function-in-node-js). — Soubhik Mondal, Nov 14 '17 at 15:48

score 0 · Answer 1 · answered Nov 14 '17 at 16:06

0

Try using async / await. Wrap your execution in a Promise to resolve the return value and reject the error value. This way you can just await on the function and get the return value. Keep in mind await stops the execution until the returned promise is fulfilled.

function getPhotoUrl(venue_id,venue_location,venue_query){
  return new Promise((resolve, reject) => {
    request({
      url: 'https://api.foursquare.com/v2/venues/'+venue_id+'/photos',
      json:true,
      method: 'GET',
      qs: {
        client_id: 'my_id',
        client_secret: 'my_secret',
        near:venue_location,
        query: venue_query,
        v: '20171114',
        limit: 1
      }
    }, function(err, res, body) {
        var result="";
        if (err)
          reject(err);     
      }
      result=body.response.photos.items[0].prefix+"300x500"+body.response.photos.items[0].suffix;
      resolve(result);
    });
  })
}

await getPhotoUrl('', '', '')

answered Nov 14 '17 at 16:06

Nandu Kalidindi

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Dear Sir where does the await happen? – Konstantinos Bolotis Nov 15 '17 at 01:38
`await getPhotoUrl('', '', '')` last line in my snippet. When you call the method. – Nandu Kalidindi Nov 15 '17 at 01:41
When i call await function, i get await is not defined. I also tried with a promise.then(), i log the data correctly but still i cannot use it and set it to a variable. – Konstantinos Bolotis Nov 15 '17 at 10:12
Check out the browser compatibility for `async/await` here https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function – Nandu Kalidindi Nov 15 '17 at 15:44

Returning undefined value - Node.js

1 Answers1