Javascript ES6 Singleton pattern with pure class

singleton.js

class Counter {

  static instance;
  static getInstance(){
    if(!Counter.instance) Counter.instance = new Counter();
    return Counter.instance;
  }

  counter = 0;
  getCount() {
    return this.counter;
  }

  increment() {
    this.counter = this.counter + 1;
    return this.counter;
  }
}

module.exports = Counter.getInstance();

singleton.new.js

//Works with new
class Counter {

  static instance;
  constructor(x){
    this.x = x
    if(!Counter.instance) Counter.instance = this;
    return Counter.instance;
  }

  counter = 0;
  getCount() {
    return this.counter;
  }

  increment() {
    this.counter = this.counter + 1;
    return this.counter;
  }
}

module.exports = Counter;