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);

console.log(null || 2 || undefined);  
console.log(1 && null && 3);  
console.log(!1 || 2 && 3);  
console.log(0 ?? 5);  
console.log(null ?? 'Привет');  

async function foo() {
  try {
    return await Promise.reject("Ошибка!");
  } catch (error) {
    console.log("Ошибка поймана:", error);
  }
}

foo().then((res) => console.log("Результат:", res));

let a = 1;  
let b = 2;  

a ??= 10;  
b ??= 20;  

console.log(a, b);  

let c = null;  
let d = undefined;  

c ??= 15;  
d ??= 25;  

console.log(c, d);

const arr = [10, 20, 30, 40];

const result = arr.reduce((acc, num) => {
  if (num > 20) {
    acc.push(num / 2);
  }
  return acc;
}, []);

console.log(result);

class Animal {}
class Dog extends Animal {}

const dog = new Dog();

console.log(dog instanceof Dog);
console.log(dog instanceof Animal);
console.log(dog instanceof Object);
console.log(dog instanceof Array);

class Animal {
  constructor(name) {
    this.name = name;
  }

  speak() {
    return `${this.name} издаёт звук.`;
  }
}

class Dog extends Animal {
  speak() {
    return "Гав-гав!";
  }
}

const dog = new Dog("Шарик");

console.log(dog.speak());
console.log(dog.name);

import React, { useState } from "react";

function App() {
  const [count, setCount] = useState(0);
  const [text, setText] = useState("");

  function increment() {
    setCount(count + 1);
  }

  function handleChange(event) {
    setText(event.target.value);
  }

  function expensiveCalculation(num) {
    console.log("Выполняем тяжелый расчет...");
    return num * 2;
  }

  const result = expensiveCalculation(count);

  return (
    <div>
      <p>Результат: {result}</p>
      <button onClick={increment}>+</button>
      <input type="text" value={text} onChange={handleChange} />
    </div>
  );
}

export default App;

function merge<T, U>(obj1: T, obj2: U): T & U {
  return { ...obj1, ...obj2 };
}

const result = merge({ name: "Анна" }, { age: 25 });

console.log(result);

const words = ["apple", "banana", "cherry"];

const result = words.filter(word => word.length > 5).map(word => word.toUpperCase());

console.log(result);