Only allow a singleton instance of a class, no matter who imports it.

implementation.js

class SomeClass {
  constructor() {
    // Does work 💪
    // Maybe this is closer to an injection pattern
    // Should have a way to remove the inject with a proper interface...
  }
}

// Singleton IIFE
// Only allow this class to instantiate once, no matter how many times it is included.
export default (Singletonizer)(SomeClass);

Singletonizer.js

const instances = {};

const Singletonizer = (Klass, ...args) => {
  const className = Klass.constructor.name;
  const created = instances.hasOwnProperty(className);
  if (!created) {
    new Klass(...args);
    instances[className] = true;
  }
}

export default Singletonizer;