1

I'm calling the google analytics API and trying to format the data I received from it on my server side before passing then to the front. Concretely I would like to use promise, to apply a map function on the response I have from the api call.

Here is my google analytics API call :

var datatable = function(req, res) {
  // authorize the client (see code above)
  authorize(function() {
    // do the actual call to the google api
    analytics.data.ga.get({
      'auth': jwtClient,
      'ids': VIEW_ID, 
      'metrics': 'ga:pageviews, ga:avgTimeOnPage',
      'dimensions': 'ga:contentGroup1, ga:searchDestinationPage',
      'start-date': '30daysAgo',
      'end-date': 'yesterday',
      'sort': '-ga:pageviews',
    }, function (err, response) {
      if (err) {
        // there was an error (unlikely, except you're trying to view a non-allowed view)
        console.log(err);
        return;
      }
      // send the data to the client (i.e. browser)
      res.send(response.rows);
    }); 
  });
}

I would like to apply the following map function map( ([x, y, z]) => ({ x, y, z }) ) using a promise (I will have more transformation to apply later on). So I've tried something like this :

const formated_data = function(req, res) {
  return datatable()
   .then(function (response, error) {
    return res.send(response.map( ([x, y, z]) => ({ x, y, z }) )
});}

I've tried various thing but most of the time I have the following error : Cannot read property 'then' of undefined. From what I have understand I know that my api call doesn't return me a promise however I don't know how I should refactor it so it return me a promise.

I'm using express so at the end I need to export my data with module.export : 

module.exports = {
    datatable
};

edit#1: I did read the answers from this post and many others and tried to apply some solutions. However I'm getting stuck with this Cannot read property 'then' of undefined. I understand why (my api call doesn't return a promise) but I don't know how to solve my issue.

Community
  • 1
  • 1
Simon Breton
  • 2,638
  • 7
  • 50
  • 105
  • If you are mapping a response (you already have the data) you don't need a promise. – yBrodsky Sep 26 '16 at 20:30
  • I only took the mapping function as an illustration here. My main goal is to lear. Also, I need to apply multiple operation like sorting data, rollup and some math or time formatting. I want to use promise to chain the function with then. – Simon Breton Sep 26 '16 at 20:36
  • Those operations are blocking. So you don't need a promise. You simply put them one after the other and they will execute in the right order. You use promises when doing some async operation (like fetching data from an API) – yBrodsky Sep 26 '16 at 20:38
  • Show us how you tried to apply the solutions from the duplicate and we can reopen and help you. – Bergi Sep 26 '16 at 21:31
  • well... based on my situation can someone tell me at least what are my callback so I can see what I need to convert as a promise. Just need some light. I've been reading and reading but I can't make the connection with my own code. – Simon Breton Sep 27 '16 at 00:18

0 Answers0