Singleton

Easy — everyone uses thisArchitecture

ELI5 — The Vibe Check

Singleton is a pattern that ensures only ONE instance of a class exists in your entire app. It's like the CEO — there's only one, everyone talks to the same person, and creating a second CEO would cause chaos. Database connections and config objects are often singletons.

Real Talk

The Singleton pattern is a creational design pattern that restricts instantiation of a class to a single object and provides a global access point to it. Often criticized for introducing global state, making testing harder and creating hidden dependencies.

Show Me The Code

class Config {
  private static instance: Config;
  private constructor() {}

  static getInstance(): Config {
    if (!Config.instance) {
      Config.instance = new Config();
    }
    return Config.instance;
  }
}

When You'll Hear This

"The logger is a Singleton — same instance everywhere." / "Singletons are controversial because they make unit testing harder."

Related Terms

Anti-Pattern

Anti-Pattern is the opposite of a design pattern — it's a commonly used approach that looks like it solves a problem but actually makes things worse.

beginnerArchitecture

Dependency Injection

Instead of your UserService creating its own DatabaseConnection (tight coupling), you pass the database in from outside: new UserService(db).

intermediateArchitecture

Design Pattern

Design patterns are like recipe cards for solving common coding problems.

intermediateArchitecture

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