我目前正在尝试编写一个简单的node.js应用程序，使用他们的API和一个围绕它设计的模块从Pokemon TCG网站获取数据。我能够从API获取信息（这将其存储在一个json风格的数组中）。然后我迭代数组，将所有文档添加到我在机器atm上运行的MongoDB容器中。
我的代码如下：

const pokemon = require('pokemontcgsdk');
var prompt = require('prompt');
var mongo = require('mongodb');

var databaseconnect = 'mongo://localhost:27017/';

prompt.start();

prompt.get(['setcodein'], function(err, result) {
    console.log(result.setcodein);
    var settosearch = result.setcodein;
    pokemon.card.where({ supertype: 'Trainer', setCode: settosearch })
    .then(results => {
        for(i =0;i < results.length;i++){
            console.log(results[i].name);
            mongo.connect(databaseconnect, function(err, db){
                var dbo = db.db("pokemon");
                dbo.collection("trainer").insertOne(result[i], function(err, r){
                    console.log('Card Added to database');
                    db.close();
                })
            })
        }
    })
});

当我运行这段代码时，我得到了以下错误;

prompt: setcodein:  sm9
sm9
Bill's Analysis
(node:5090) DeprecationWarning: current URL string parser is deprecated, and will be removed in a future version. To use the new parser, pass option {
 useNewUrlParser: true } to MongoClient.connect.
Unhandled rejection TypeError: Cannot read property 'db' of null
    at /Users/elliottbuckingham/Google Drive/Coding/Java/Pokemon App/index.js:19:30
    at err (/Users/elliottbuckingham/Google Drive/Coding/Java/Pokemon App/node_modules/mongodb/lib/utils.js:415:14)
    at executeCallback (/Users/elliottbuckingham/Google Drive/Coding/Java/Pokemon App/node_modules/mongodb/lib/utils.js:404:25)
    at executeOperation (/Users/elliottbuckingham/Google Drive/Coding/Java/Pokemon App/node_modules/mongodb/lib/utils.js:422:7)
    at MongoClient.connect (/Users/elliottbuckingham/Google Drive/Coding/Java/Pokemon App/node_modules/mongodb/lib/mongo_client.js:168:10)
    at Function.MongoClient.connect (/Users/elliottbuckingham/Google Drive/Coding/Java/Pokemon App/node_modules/mongodb/lib/mongo_client.js:372:22)
    at pokemon.card.where.then.results (/Users/elliottbuckingham/Google Drive/Coding/Java/Pokemon App/index.js:18:19)
    at tryCatcher (/Users/elliottbuckingham/Google Drive/Coding/Java/Pokemon App/node_modules/bluebird/js/release/util.js:16:23)
    at Promise._settlePromiseFromHandler (/Users/elliottbuckingham/Google Drive/Coding/Java/Pokemon App/node_modules/bluebird/js/release/promise.js:51
2:31)
    at Promise._settlePromise (/Users/elliottbuckingham/Google Drive/Coding/Java/Pokemon App/node_modules/bluebird/js/release/promise.js:569:18)
    at Promise._settlePromise0 (/Users/elliottbuckingham/Google Drive/Coding/Java/Pokemon App/node_modules/bluebird/js/release/promise.js:614:10)
    at Promise._settlePromises (/Users/elliottbuckingham/Google Drive/Coding/Java/Pokemon App/node_modules/bluebird/js/release/promise.js:694:18)
    at _drainQueueStep (/Users/elliottbuckingham/Google Drive/Coding/Java/Pokemon App/node_modules/bluebird/js/release/async.js:138:12)
    at _drainQueue (/Users/elliottbuckingham/Google Drive/Coding/Java/Pokemon App/node_modules/bluebird/js/release/async.js:131:9)
    at Async._drainQueues (/Users/elliottbuckingham/Google Drive/Coding/Java/Pokemon App/node_modules/bluebird/js/release/async.js:147:5)
    at Immediate.Async.drainQueues [as _onImmediate] (/Users/elliottbuckingham/Google Drive/Coding/Java/Pokemon App/node_modules/bluebird/js/release/async.js:17:14)
    at runCallback (timers.js:705:18)
    at tryOnImmediate (timers.js:676:5)
    at processImmediate (timers.js:658:5)

我试过不同的连接方法。我也试过添加err throw，但错误出来或多或少是一样的。
口袋妖怪数据库和训练器集合都创建好了。但是数据库里没有文档。
我做了件很明显的错事
亲切问候Elliott