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Design Pattern

Singleton

Ensure only one shared instance exists for a resource.

creational

Visual Diagram

getInstance()
-> exists? return same
-> missing? create once

When To Use

  • ->DB connection pool shared across the app
  • ->Config loaded once at startup
  • ->Logger with one output stream
  • ->Shared in-memory cache
Used in: Mongoose connection, Winston logger, config manager
singleton.js

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