Using fat arrow functions will change what this refers to. __v is the versionKey property set on each document when first created by Mongoose. Its value contains the internal revision of the document. ‘Documents’ are equivalent to records or rows of data in SQL. While a SQL row can reference data in other tables, Mongo documents usually combine that in a document. ‘Collections’ in Mongo are equivalent to tables in relational databases.
One additional consideration is there are cases where you may not want to close the connection. Since opening and closing connections are relatively expensive high volume applications might want to use connection pooling to reuse connections rather than continually opening and closing new ones. You huffy mountain bike may have noticed that in the first .then function the value of db was saved to a variable called accountDb. This was done in anticipation of it being needed later in the application logic to close the connection. This was necessary since the scope of db is limited to that first .then function.
Powered by Typescript, NestJS offers complete support for databases like MySQL, PostgreSQL, and MongoDB. Using the NestJS Mongoose package, you can easily connect to the MongoDB database and build scalable applications. Mongoose is one of the popular MongoDB object modeling tools. First, by defining our model, we are explicitly telling our Node.js application what fields and data types we’ll allow to be inserted into a specific collection. For example, our Mongoose Blog schema defines atitle property of type String. If we were to try and insert a blog post with a title property that was an array, it would fail.
In the example above this is done by calling the accountsDb.close() function to stop the connection and free up any resources devoted to it. In the early 1980’s a new type of database based on the Structured Query Language began to take hold. The main advantage of a SQL database had over a CODASYL database is that manipulating data was simpler since data in a SQL database is organized relationally rather than physically. This meant that application programs became simpler to write and maintain. The require(‘mongoose’) call above returns a Singleton object. It means that the first time you call require(‘mongoose’), it is creating an instance of the schwinn bicycles class and returning it.
That subsequent database requests will be issued through. The first such request is mongoClient.connect which creates the connection and returns a reference to the client instance. Pre-built, enterprise-class, full-user security with single sign-on, schwinn bicycles automatically publishes for both browser and mobile interfaces. With your business objects and logic shared across all device types, creating a mobile or tablet version of your app is simple, fast, and hassle-free. We have barely scratched the surface exploring some of the capabilities of Mongoose.