function sayHi() {
  console.log(name);
  console.log(age);
  var name = "John";
  let age = 30;
}

sayHi();

const arr = [1, 2, 3];

arr.push(4);
arr[0] = 0;

try {
  arr = [5, 6, 7];
} catch (error) {
  console.log(error.message);
}

console.log(arr);

console.log(1 + "2" + "3");
console.log(1 + +"2" + "3");
console.log(1 + -"1" + "2");
console.log("2" * "3");
console.log("4" / "2");
console.log("4" + "2");

const obj = {
  a: 1,
  b: function() {
    return this.a;
  }
};

const fn = obj.b;
console.log(obj.b());
console.log(fn());

console.log(typeof null);
console.log(null == undefined);
console.log(null === undefined);
console.log(null > 0);
console.log(null >= 0);

setTimeout(() => console.log("Timeout"), 0);

Promise.resolve().then(() => console.log("Promise"));

console.log("Sync");

<div>
  <p>Параграф 1</p>
  <p>Параграф 2</p>
  <p>Параграф 3</p>
</div>
<noscript>
  const div = document.querySelector('div');
  console.log(div.innerHTML);
</noscript>

p {
  color: blue !important;
}

.container p {
  color: red;
}

p.special {
  color: green;
}

<div class="container">
  <p class="special">Привет!</p>
</div>

const promise = new Promise((resolve, reject) => {
  console.log("Промис создан");
  resolve("Успех!");
});

promise.then((result) => console.log(result));
console.log("Код завершён");

const numbers = [1, 2, 3, 4, 5];
const sum = numbers.reduce((acc, curr) => acc + curr, 0);

console.log(sum);

try {
  const num = 10 / 0;
  if (!isFinite(num)) {
    throw new Error("Деление на ноль!");
  }
} catch (error) {
  console.log(error.message);
} finally {
  console.log("Операция завершена");
}

const age = 30;
type AgeType = typeof age; // number

onst user = {
  name: "Alice",
  age: 25,
};

type UserType = typeof user;

type UserKeys = keyof UserType; // "name" | "age"

function printUserInfo(key: UserKeys) {
  console.log(key);
}

printUserInfo("name"); // ✅ Работает
// printUserInfo("email"); // ❌ Ошибка, такого ключа нет

const user = {
  id: 1,
  name: "Alice",
  isAdmin: true,
};

type UserKeys = keyof typeof user;

let key: UserKeys;

const promise = new Promise((resolve, reject) => {
  console.log("Начало");
  resolve("Успех");
});

promise
  .then((result) => {
    console.log(result);
    return "Следующий then";
  })
  .finally(() => {
    console.log("Финально");
  })
  .then((data) => {
    console.log(data);
  });

console.log("Конец");

const numbers = [1, 2, 3, 4, 5];

const result = numbers.map(num => {
  if (num % 2 === 0) {
    return num * 2;
  }
});

console.log(result);