Factory Functions & Singleton Pattern

What pattern does this approach demonstrate?

function createShape(type) {
  if (type === 'circle') {
    return function(radius) {
      return {
        type: 'circle',
        radius,
        area: () => Math.PI * radius * radius
      };
    };
  } else if (type === 'rectangle') {
    return function(width, height) {
      return {
        type: 'rectangle',
        width,
        height,
        area: () => width * height
      };
    };
  }
}

Prototype chain
Factory of factories
This demonstrates a factory of factories pattern: 1) The outer function creates specialized factory functions based on parameters, 2) Each returned factory function creates specific types of objects, 3) This allows for organizing related object creation by type, 4) It enables more specific factory functions with tailored parameters, 5) This pattern is useful for complex object hierarchies with different creation requirements, 6) It follows the principle of single responsibility by separating object type determination from actual object creation.
Mixin pattern
Observer pattern

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