ES6 Function based OOP design

function.js

function Counter(startingCount) {
  this.startingCount = startingCount;
  this.count = this.startingCount;

  this.increment = () => {
    this.count = this.count + 1;
  };

  this.decrement = () => {
    this.count = this.count - 1;
  };

  this.reset = () => {
    this.count = this.startingCount;
  };

  this.getCount = () => {
    return this.count;
  };
}

const my_counter = new Counter(100);

my_counter.increment();
my_counter.increment();
my_counter.increment();
my_counter.decrement();

console.log(my_counter.getCount());

my_counter.reset();

console.log(my_counter.getCount());