Cannot read property 'join' of null error with node and GA analytics api

Question

I'm trying to use Google Analytics Core Reporting API from Node.js by following this tutorial http://www.2ality.com/2015/10/google-analytics-api.html. I'm launching the script directly from my terminal with babel-node mygaapiscript.js. but I've got the following error :

  /Users/me/Desktop/dashboard/dashboard-ga/node_modules/gtoken/lib/index.js:160
        this.scope = options.scope.join(' ');
                                  ^

    TypeError: Cannot read property 'join' of null
        at GoogleToken._configure (/Users/me/Desktop/dashboard/dashboard-ga/node_modules/gtoken/lib/index.js:160:31)
        at new GoogleToken (/Users/me/Desktop/dashboard/dashboard-ga/node_modules/gtoken/lib/index.js:19:8)
        at JWT.GoogleToken [as gToken] (/Users/me/Desktop/dashboard/dashboard-ga/node_modules/gtoken/lib/index.js:17:12)
        at JWT._createGToken (/Users/me/Desktop/dashboard/dashboard-ga/node_modules/google-auth-library/lib/auth/jwtclient.js:218:24)
        at JWT.refreshToken_ (/Users/me/Desktop/dashboard/dashboard-ga/node_modules/google-auth-library/lib/auth/jwtclient.js:133:15)
        at JWT.authorize (/Users/me/Desktop/dashboard/me-MacBook-Pro:routes

What does this error mean ?

here is my script :

#!/usr/bin/env babel-node
import google from 'googleapis';
'use strict';

import key from './client_id.json';
const VIEW_ID = 'ga:70810323';

let jwtClient = new google.auth.JWT(
    key.client_email, 
    key.private_key,
    ['https://www.googleapis.com/auth/analytics.readonly'],null);

    jwtClient.authorize(function (err, tokens) {
      if (err) {
        console.log(err);
        return;
      }
      let analytics = google.analytics('v3');
      queryData(analytics);
    });

    function queryData(analytics) {
      analytics.data.ga.get({
        'auth': jwtClient,
        'ids': VIEW_ID,
        'metrics': 'ga:uniquePageviews',
        'dimensions': 'ga:pagePath',
        'start-date': '30daysAgo',
        'end-date': 'yesterday',
        'sort': '-ga:uniquePageviews',
        'max-results': 10,
      }, function (err, response) {
        if (err) {
          console.log(err);
          return;
        }
        console.log(JSON.stringify(response, null, 4));
      });  
    }

module.exports = {queryData};

Got the module.exports because I'm using it inside express.

Answer 1

Your arguments to google.auth.JWT() seem to be wrong. See the example in the documentation and the JWT example in the googleapis repo here. The third argument should be the literal key data if you are not passing a key filename for the second argument. So just add null for the third argument:

let jwtClient = new google.auth.JWT(
  key.client_email, 
  key.private_key,
  null,
  ['https://www.googleapis.com/auth/analytics.readonly'],
  null
);