// What will be logged when this code runs?
const counter = (() => {
  let count = 0;
  
  return {
    increment() {
      count += 1;
      return this;
    },
    reset() {
      count = 0;
      return this;
    },
    get value() {
      return count;
    }
  };
})();

const { increment, value } = counter;

increment();
counter.increment();

console.log(value);

function processConfig(config) {
  const defaultPort = 8080;
  const defaultTimeout = 5000;
  
  const port = config?.port ?? defaultPort;
  const timeout = config?.timeout ?? defaultTimeout;
  const debug = config?.debug ?? false;
  
  return { 
    summary: `Port: ${port}, Timeout: ${timeout}, Debug: ${debug ? 'enabled' : 'disabled'}`,
    isUsingDefaults: port === defaultPort && timeout === defaultTimeout
  };
}

const result = processConfig({ port: 0, timeout: null });
console.log(result.summary);

function processUserData(data) {
  const settings = {
    theme: data.preferences?.theme ?? 'light',
    notifications: data.preferences?.notifications ?? true,
    fontSize: data.preferences?.fontSize ?? 16
  };
  
  let status = data.status ?? 'active';
  let reputation = data.reputation ?? 0;
  
  console.log(reputation || 'No reputation yet');
  return settings;
}

processUserData({ status: '', reputation: 0 });

type User = {
  id: number;
  name: string;
  email?: string;
};

function processUser<T extends User>(user: T): T & { processed: boolean } {
  return { ...user, processed: true };
}

const partialUser = { id: 1, name: 'Alice' };
const result = processUser(partialUser);

console.log(typeof result.email);

const num1 = 9007199254740992n;
const num2 = 1n;

const result1 = num1 + num2;
const result2 = Number(num1) + Number(num2);
const result3 = num1 + BigInt(1);
const result4 = String(num1) + String(num2);

console.log(typeof result2 === typeof result1, result1 === result3, result4);

function createSymbolDemo() {
  const obj = {};
  
  const sym1 = Symbol('description');
  const sym2 = Symbol('description');
  const sym3 = Symbol.for('shared');
  const sym4 = Symbol.for('shared');
  
  obj[sym1] = 'Value 1';
  obj[sym2] = 'Value 2';
  obj[sym3] = 'Value 3';
  obj[sym4] = 'Value 4';
  
  console.log(Object.keys(obj).length, sym1 === sym2, sym3 === sym4, obj[sym3]);
}

createSymbolDemo();

function* generateSequence() {
  let i = 1;
  while (i <= 3) {
    yield i++;
  }
}

function* extendSequence() {
  yield* generateSequence();
  yield* [4, 5];
  yield 6;
}

const generator = extendSequence();
const result = [];

for (const value of generator) {
  if (value % 2 === 0) {
    result.push(value * 2);
  } else {
    result.push(value);
  }
}

console.log(result);