tracking.js

var Twitter = require('twitter');
var client = new Twitter(/*pass auth keys*/);

function startTracking(topic){
  var isTweet = obj => obj && typeof obj.id_str === 'string' &&
      typeof obj.text === 'string' && obj.place &&
      obj.place.country_code === "US" && obj.place.place_type === "city";
  var handleTweet = tweet => {
    if(isTweet(tweet)){
      topic.publish({
        data : tweet,
        attributes : {created_at : tweet.created_at}
      }, function(err, messageIds, apiResponse){
        if(err)
          return console.log("Error publishing : %s", err);
        console.log("Message %s published", messageIds)
      });
    }
  }
  client.stream('statuses/filter', {track: 'Trump,Hillary,Clinton,debate'},  function(stream) {
    stream.on('data', handleTweet);
    stream.on('error', console.log);
  });
}