/* jshint esnext: true */

var generateId = function() {

  this.id = this.id ? this.id + 1 : 1;

  return this.id;

}

​

var Person = class {

  constructor(first, last) {

    this.first = first;

    this.last = last;

    this.id = generateId();

  }

  toString() {

    return this.id + ' ' + this.first + ' ' + this.last;

  }

};

​

var Employee = class extends Person {

    isManager() {

      return false;

    }

}

​

var alice = new Person('Alice', 'Seasons');

console.log(alice.toString());

​

var developer = new Employee('Kevin', 'Nice');

console.log(developer.toString());

console.log(developer.isManager());