update.js

const express = require('express');
const XMLHttpRequest = require("xmlhttprequest").XMLHttpRequest;
const bodyParser = require('body-parser');
const cors = require('cors');
const assert = require('assert');
const util = require('util');

const MongoClient = require('mongodb').MongoClient;
const mongo = require('mongodb');
const mongoose = require('mongoose');
const dbName = 'heroku_wlmwvdfs';

require("dotenv").config();
const KEY = process.env.KEY; //API Key
const MONGODB_URI = process.env.MONGODB_URI;

function update() {
    let xhr = new XMLHttpRequest();
    // const client = new MongoClient(MONGODB_URI);
    console.log("MONGODB_URI " + MONGODB_URI);
    const client = new MongoClient(MONGODB_URI);

    client.connect(function(err) {
      assert.equal(null, err);
      console.log("MongoDB update Connected...");
      let maxPage = 4;

      const db = client.db(dbName)
      // console.log(db.__proto__);
      const collection = db.collection('topArtists');
      // Insert some documents

      let url = "http://ws.audioscrobbler.com/2.0/?method=chart.gettopartists&api_key=" +
          KEY + "&format=json&limit=500&page=1";
      xhr.open("GET", url, false);
      xhr.onload = function () {
          let json = JSON.parse(this.responseText);
          json['artists']['artist'].forEach((item) => {

              collection.updateOne({ name: item.name.toLowerCase() }
                  , { $push: { listeners : item.listeners } }, function(err, result) {
                  assert.equal(err, null);
                  // console.log(util.format("Updated the document with the field %s equal to %d", item.name.toLowerCase(), item.listeners));
                });

              // collection.insertOne({name: item.name.toLowerCase(), listeners: [item.listeners]}, function(err, r) {
              //   assert.equal(null, err);
              //   assert.equal(1, r.insertedCount);
              //   });
          });
      };
      xhr.send();
      client.close();
    });
}
module.exports = update;