Simplest/Cleanest way to implement singleton in JavaScript?

Question

What is the simplest/cleanest way to implement singleton pattern in JavaScript?

Answer 1

Simplest/Cleanest for me means also simply to understand and no bells & whistles as are much discussed in the Java version of the discussion:

What is an efficient way to implement a singleton pattern in Java?

The answer that would fit simplest/cleanest best there from my point of view is:

https://stackoverflow.com/a/70824/1497139

And it can only partly be translated to JavaScript. Some of the difference in Javascript are:

• constructors can't be private
• Classes can't have declared fields

But given latest ECMA syntax it is possible to get close with:

Singleton pattern as JavaScript class example

 class Singleton {

  constructor(field1,field2) {
    this.field1=field1;
    this.field2=field2;
    Singleton.instance=this;
  }

  static getInstance() {
    if (!Singleton.instance) {
      Singleton.instance=new Singleton('DefaultField1','DefaultField2');
    }
    return Singleton.instance;
  }
}

Example Usage

console.log(Singleton.getInstance().field1);
console.log(Singleton.getInstance().field2);

Example Result

DefaultField1
DefaultField2