Getting undefined for function call in Express render()

Question

I'm new to Node and Express, and am running into trouble getting data from one function, to pass into another function as a var. I presume that this is because I am not handling the callback and async stuff properly, but would appreciate a steer.

The code should hopefully be explanatory. I am attempting to retrieve some JSON data from a URL, and pass it to the router.get function's render() method. However, nothing ("undefined") gets sent instead. When I run the getData() function separately, however, it returns the correct data, so as stated, I presume this is because I'm not handling the async stuff correctly.

function getData(cid){
   var request = require("request");
   var cid ='XXXXXX' // hard code temp
   var baseUrl = "someurl.com"
   var apiKey = "XXXXXX"
   var cUrl = baseUrl+cid+'?api_key='+apiKey


  request({
    url: cUrl,
    json: true
  }, function (error, response, body) {

    if (!error && response.statusCode === 200) {
      console.log(body._embedded.assets); //Print the json response
      return body._embedded.assets
    }
  });
}

/* GET home page. */
router.get('/', function(req, res) {

  var LiveCards = getData()
  var cID = (req.query.cID
            ? req.query.cID
            : '14d115ff-1db7-4a6f-8648-ea64bc1a6597')
  var limit = Number(req.query.limit)

  res.render('index', {
      title: 'Cards',
      cards: LiveCards.slice(0,limit), <--- returning undefined at the moment
      limit: limit,
      activateSharetools: activateSharetools,
      cID: cID,
      cardsHeader: req.query.cardsHeader,
   });
});

Any guidance appreciated.

There is no return from getData(); LiveCards will be `undefined`. — Sam Greenhalgh, Dec 16 '14 at 09:29
hmm. ok. I'm trying to `return body._embedded.assets`. Is that not going to return the data? — The Pied Pipes, Dec 16 '14 at 09:31
No, it's not going to return the data. Your `get_data` function does not have any `return` statement in it. When you run the function separately, you only see the `console.log` but not the return value. — Bergi, Dec 16 '14 at 09:33

score 1 · Accepted Answer · answered Dec 16 '14 at 09:30

request is asynchronous function, you need add callback to get Data and execute it after completes the request, like this:

function getData (cid, callback) {
   var request = require("request");
   var cid     = 'XXXXXX';
   var baseUrl = "someurl.com";
   var apiKey  = "XXXXXX";
   var cUrl    = baseUrl + cid + '?api_key=' + apiKey

  request({url: cUrl, json: true}, callback);
}

router.get('/', function (req, res) {
  var cID   = req.query.cID ? req.query.cID : '14d115ff-1db7-4a6f-8648-ea64bc1a6597');
  var limit = Number(req.query.limit);

  getData(cID, function (error, response, body) {
    if (!error && response.statusCode === 200) {
      res.render('index', {
        title: 'Cards',
        cards: body._embedded.assets.slice(0, limit), <--- returning undefined at the moment
        limit: limit,
        activateSharetools: activateSharetools,
        cID: cID,
        cardsHeader: req.query.cardsHeader,
      });
    } else {
      throw error;
    }
  });
});

Getting undefined for function call in Express render()

1 Answers1