static methods and params for class

static.js

class Item {
  constructor() {
    this.id = Item.count++;
  }
}

Item.count = 0;
Item.getCount = function() {
  return this.count;
};

class Model extends Item {
  constructor(name) {
    super();
    this.name = name;
  }
}

console.log(new Model('nissan'));
console.log(new Model('mazda'));

console.log(Item.getCount());

/*
{ id: 0, name: 'nissan' }
{ id: 1, name: 'mazda' }
2
*/