firstDemo.js

Array.prototype.first = function(propertySelector = obj => obj) {
  return this.filter(propertySelector)[0];
};

function firstDemo(orders) {
  const firstOrderAfterMarch = orders.first(order => order.orderDate >= march);
  printHeaderFooter(
    "First order after March",
    () => printOrder(firstOrderAfterMarch, indentBy),
    indentBy
  );

  const firstOrderAfterSeptember =
    orders.first(order => order.OrderDate >= september) || null;
  printHeaderFooter(
    "First or Default order after September",
    () => printOrder(firstOrderAfterSeptember, indentBy),
    indentBy
  );
}