auth.js

var request = require('request');
var graph = require('@microsoft/microsoft-graph-client');
var Q = require('q');

// The auth module object.
var auth = {};

auth.getAccessToken = function (tenantId) {
  var deferred = Q.defer();
  var requestParams = {
    grant_type: 'client_credentials',
    client_id: process.env.ClientId,
    client_secret: process.env.ClientSecret,
    scope: 'https://graph.microsoft.com/.default'
  };

  var url = "https://login.microsoftonline.com/" + tenantId + "/oauth2/v2.0/token";
  request.post({ url: url, form: requestParams }, function (err, response, body) {
    var parsedBody = JSON.parse(body);

    if (err) {
      deferred.reject(err);
    } else if (parsedBody.error) {
      deferred.reject(parsedBody.error_description);
    } else {
      // If successful, return the access token.
      deferred.resolve(parsedBody.access_token);
    }
  });

  return deferred.promise;
};

module.exports = auth;