First of all, let’s start with an explanation of what design patterns are. In the simplest terms, they allow us to re-use code for re-occurring problems. Instead of solving the same problems again and again, we can re-use efficient code that already works. Why would you use design patterns? The reasons are that they are:

• Well documented and tested
• Reusable in many different situations
• Efficient
• Saving you time

There are three types of design patterns:

1. Creational - the creation of the object instances
2. Structural - the way the objects are designed
3. Behavioural - how objects interact with each other

The Creational Design Patterns covered in the article are:

1. Singleton
2. Factory
3. Builder
4. Prototype

These are the two ways of implementing the Singleton pattern in NodeJS. To recap:

• Singleton is useful when you want only one instance of a class.
• In NodeJS, we can make use of the module caching system to export an instance directly.

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