Discussion on: Singleton in JavaScript

[Avalander]

That's not what I would define as inheriting, you're cloning the object and adding extra properties to the clone. Nothing prevents anyone from cloning your singleton instance either, though, as long as they remember to carry on the prototype.

const clone = Object.assign(
    Object.create(SingletonClass.prototype),
    instanceOne,
    { shoutName() { return this.name.toUpperCase() }}
)

console.log(clone.shoutName())

[Tomasz Buszewski]

You are completely right, but here you are stepping away from the merit of the text, which is singleton design pattern. In JavaScript all (or are there some that aren't?) reference types can be cloned and those cloned modified.