Factory Functions & Singleton Pattern

What encapsulation pattern does this API factory implement?

function createAPI() {
  const privateData = {};
  
  function privateMethod() {
    // Implementation
  }
  
  return {
    publicMethod() {
      privateMethod();
      return 'result';
    },
    getData(key) {
      return privateData[key];
    },
    setData(key, value) {
      privateData[key] = value;
    }
  };
}

Mixin pattern
Singleton pattern
Module pattern with private members
This factory function implements the module pattern with private members: 1) It uses closures to create private state and methods, 2) Only selected functionality is exposed through the returned object, 3) privateData and privateMethod are not accessible from outside, 4) It achieves information hiding and encapsulation, 5) The public API is clearly defined by the returned object, 6) This pattern is commonly used for creating modules with clean public interfaces while hiding implementation details.
Decorator pattern

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