function checkTDZ() {
  console.log(typeof undeclaredVar);

  try {
    console.log(typeof letVar);
  } catch (e) {
    console.log(`Caught: ${e.constructor.name}`);
  }

  let letVar = "initialized";

  const result = (() => {
    let x = 10;
    return function () {
      let x = x + 5;
      return x;
    };
  })();

  try {
    console.log(result());
  } catch (e) {
    console.log(`Caught: ${e.constructor.name}`);
  }
}

checkTDZ();