{
  const firstName = 'John';

  // if (firstName === John) {
  //   // ReferenceError: John is not defined
  //   console.log(firstName);
  // }

  // if (firstname === 'John') {
  //   // Uncaught ReferenceError: firstname is not defined
  //   console.log(firstName);
  // }

  if (firstName === 'John') {
    console.log(firstName);
  }

  function greet() {
    console.log('Hello, ' + fullName); // Cannot find name 'fullName'.
    console.log(typeof fullName);
  }

  // greet(); // => ReferenceError: fullName is not defined

  // function greet(fullName) {
  //   console.log(`Hello, ${fullName}`);
  // }

  greet('John Wick');

  // function divide(a, b) {
  //   return a / b;
  // }

  // console.log(divide(10)); // Expected 2 arguments, but got 1.
}