Question

mongodb的新手，但我认为必须有一些我没有得到的非常基本的东西。如果运行外壳程序并键入db.questions.count()，则得到1，即在外壳程序中创建的1。但是，如果我在应用程序中执行相同的操作：

...
const MONGO_URL = 'mongodb://127.0.0.1:27017/';
const {MongoClient, ObjectId} = mongo;

const run = async () => {
  try {
    const db = await 
    MongoClient.connect(MONGO_URL);

    const Questions = db.questions; 
    console.log(Questions.count()); 
...

我得到Cannot read property 'count' of undefined。为什么是这样？

对于它的价值，定义了db，并且URL与shell中的URL是相同的。再加上服务器启动正常，所以我认为这意味着mongodb实例运行正常。

Answer 1

安装“ mongodb” npm模块。它是NodeJ的官方MongoDB客户。

// Create a Mongo Client Instace to connect to the MongoDB Database
// and perform various functions.
const MongoClient = require( 'mongodb' ).MongoClient;
// Store the URL of your MongoDB Server
const mongoURL = "mongodb://localhost:27017/";
// Stored the name of the Database you wanna connect to.
const dbName = "testdb";

// Create a new Mongo DB client that will connect to the MongoDB Server.
const client = new MongoClient(mongoURL);

// Connect the Client to the MongoDB Server.
client.connect( (err) => {

    // Error handling of some sort.
    if(err) throw err;

    console.log( 'connected!' );

    // Connect to the database you want to manage using the dbName you
    // stored earlier.
    const db = client.db( dbName );

    // Store the name of the collection you want to read from.
    // this can be created above near the dbName.
    const collectionName = "testCol"

    // Connect to the collection that you stored above.
    const collection = db.collection( collectionName );

    // Query the MongoDB database and log the results, if any.
    collection.find({}).toArray( (err, docs) => {
        console.log(docs);
    } );

} )

要摆脱该newURLParser错误，只需使用

const client = new MongoClient( mongoURL, { useNewUrlParser: true } );

代替

const client = new MongoClient(mongoURL);

这是指向MongoDB NodeJS快速入门的链接。 http://mongodb.github.io/node-mongodb-native/3.1/quick-start/quick-start/

为什么我看不到我的应用程序中的Mongodb集合？

1 个答案: