javascript - Returning undefined value - Node.js

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; 
    }
  );
}