JavaScript Design Patterns
Nairi Harutyunyan / nairihar
Node.js Armenia Community
Backend Engineer / Screenful
#nodejsarmenia 💚
t.me/nodejsarmenia
About me
Why Design Patterns?
What is Design Pattern?
*Design Patterns
*Singleton
*Factory
*Middleware
*Command
*Observer
*Module
*Adapter
*Strategy
*Pub/Sub
*Constructor
Singleton
Restricts the instantiation of a class to one single* instance
Factory
Creates objects without specifying the exact class
Module
Similar to a singleton, it has only one instance and exposes its members, but it doesn’t have any kind of internal state
Constructor
Allows to create multiple instances of the same script or plugin
Adapter
Allows us to us access the functionality of an object using a different interface
Adapter
Adaptee
methodA()
methodB()
methodD()
methodC()
Strategy
Encapsulates an algorithm inside a class/function separating the selection from the implementation
Observer
A way of notifying change to a number of Subjects
Pub/Sub
A way of publishing notification to a number of subscribers
Observer
Subscriber
Publisher
Broker
Subscriber
subscribe
notify
Command
Encapsulate a command request as an object to enable, logging and/or queuing of requests, and provides error-handling for unhandled requests
Middleware
Functions that have access to the request object {req}, the response object {res}, and the (next) middleware function
Middleware 1
request {}
response {}
next ()
Middleware 2
request {}
response {}
next ()
Middleware3
request {}
response {}
next ()
Error ...
response object
response object