Connecting to a MongoDB Database by Using Mongoose

Connecting to a MongoDB database by using Mongoose is very similar to using the connection string method discussed in Chapter 13, “Getting Started with MongoDB and Node.js.” It uses the connection string format and options syntax shown below:

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connect(uri, options, [callback])

The connect() method is exported at the root level of the mongoose module. For example the following code connects to the words database on the localhost:

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var mongoose = require('mongoose'),
mongoose.connect('mongodb://localhost/words'),

The connection can be closed using the disconnect() method of the mongoose module. For example:

mongoose.disconnect();

Once created, the underlying Connection object can be accessed in the connection attribute of the mongoose module. The Connection object provides access to the connection, underlying Db object, and Model object that represents the collection. This gives you access to all the Db object functionality described in Chapter 13. For example, to list the collections on the database, you could use the following code:

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mongoose.connection.db.collectionNames(function(err, names){
  console.log(names);
});

The Connection object emits the open event, which you can use to wait for the connection to open before trying to access the database. To illustrate the basic life cycle of a MongoDB connection via Mongoose, the code in Listing 16.1 imports the mongoose module, connects to the MongoDB database, waits for the open event, displays the collections in the database, and disconnects. The output is shown in Figure 16.1.

Listing 16.1 mongoose_connect.js: Connecting to a MongoDB database by using Mongoose

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1 var mongoose = require('mongoose'),
2 mongoose.connect('mongodb://localhost/words'),
3 mongoose.connection.on('open', function(){
4   console.log(mongoose.connection.collection);
5   mongoose.connection.db.collectionNames(function(err, names){
6     console.log(names);
7     mongoose.disconnect();
8   });
9 });

Figure 16.1 Connecting to a MongoDB database by using Mongoose.