How to define Singleton in TypeScript

What is the best and most convenient way to implement a Singleton pattern for a class in TypeScript? (Both with and without lazy initialisation).

Singleton classes in TypeScript are generally an anti-pattern. You can simply use namespaces instead.

Useless singleton pattern

class Singleton {
    /* ... lots of singleton logic ... */
    public someMethod() { ... }
}

// Using
var x = Singleton.getInstance();
x.someMethod();

Namespace equivalent

export namespace Singleton {
    export function someMethod() { ... }
}
// Usage
import { SingletonInstance } from "path/to/Singleton";

SingletonInstance.someMethod();
var x = SingletonInstance; // If you need to alias it for some reason

Stack Overflow Q#30174078, score: 111