global.js

// Constructor function
// Not to be used as normal function
function Person(id, name) {

  // Was this set to global?
  if (this == global)
    throw "Error: use 'new Person()'";

  this.id = id;
  this.name = name;
}

// Expect error here
// let result = Person(1, "Brendan");

function Visitor(id, name, visiting) {
  Person.call(this, id, name);
  this.visiting = visiting;
}

let ryan = new Visitor(2, "Dahl", "Eich");