Chapter 11. Plugins – Re-using Code

In this chapter, we will introduce the Mongoose plugin architecture and see how we can use it to create modular re-usable code. We will look at the syntax and how to write them and include them in our code.

By the end of this chapter, you will understand how to create and use Mongoose plugins. You will also know where to go to find existing plugins that others have written, and contribute to the community by submitting your own. You will have created some plugins in the MongoosePM application.

Reusable schema plugins

If we look at our schemas, we can see some common elements that we are repeating. For example, each of our schemas has an identical modifiedOn path, and our project and task schemas each have identical createdBy and createdOn paths.

If you're at all familiar with the DRY (Don't Repeat Yourself) principle of coding, you'll probably want to tidy these bits up and just declare them once. This is where the Mongoose plugin architecture comes in.

Creating a schema plugin

Let's start by creating a schema extension for adding createdOn and createdBy. Inside our model/db.js file, we can add the following code, preferably above the definitions for our two schemas:

var creationInfo = function creationInfo (schema, options) {
  schema.add({createdOn: { type: Date, default: Date.now }});
  schema.add({createdBy: { type: mongoose.Schema.Types.ObjectId, ref: 'User', required: true}});
};

This exposes a function that will allow us to plug in the paths createdOn and createdBy, to some...

Sharing with the community

Mongoose plugins are not just re-usable for you, you can share them with the rest of the community. By packaging them up as npm modules, and tagging them with "mongoose", they will become available in the Mongoose plugins directory.

There are already a large number of community-submitted plugins available that include adding support for a long number SchemaType, validation helpers, and authentication and user management plugins.

You can find the directory, and submission guidelines at the following link:

http://plugins.mongoosejs.com

Summary

In this chapter, we've seen how we can take repeated paths from our schemas and turn them into a single Mongoose plugin. We've learned how to create them as separate files, include them in our application, and also use schema middleware to set data on a save operation. We have used all of this knowledge to create plugins and add them to our MongoosePM application, tidying up our code and removing repetition.

This is the final chapter of Mongoose for Application Development. By now you should have the tools and understanding to enable you to build a web application based on everything Mongoose has to offer. I'm sure that by now you will agree that Mongoose is a very useful addition to the Node.js and MongoDB technology stack.