Object Creation Methods

Which creational pattern ensures only one instance exists?

const Singleton = (() => {
  let instance;
  
  function createInstance() {
    return {
      data: [],
      add(item) { this.data.push(item); }
    };
  }
  
  return {
    getInstance() {
      if (!instance) {
        instance = createInstance();
      }
      return instance;
    }
  };
})();

Factory Pattern
Module Pattern
Singleton Pattern
This implements the Singleton pattern: 1) Uses closure to maintain private instance, 2) Creates instance only on first request, 3) Returns same instance for all subsequent calls, 4) Provides global point of access, 5) Ensures single source of truth, 6) Common for managing shared resources or state.
Constructor Pattern

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