mandatory_parameters.js

const error_handler = (property) => {
  throw new Error(`Error: ${property} is required!`);
}

const monitor_roads = (car=error_handler('Car'), speed=error_handler('Speed')) => {
  console.log(`Your ${car} was going at a speed of ${speed}mph.`);
}

monitor_roads('Ferrari', 240); // Your Ferrari was going at a speed of 240mph.
monitor_roads('Ferrari'); // Error: Speed is required!