const inventory = {
  apples: 5,
  bananas: 0,
  cherries: 12,
  dates: undefined,
  elderberries: null,
};

const summary = Object.entries(inventory)
  .filter(([_, value]) => value)
  .reduce((acc, [key, value]) => {
    acc[key] = value * 2;
    return acc;
  }, {});

console.log(Object.keys(summary).length);
console.log(Object.values(summary).every(v => v > 10));
console.log(Object.keys(inventory).length === Object.keys(summary).length);

const user = {
  profile: {
    name: "Alice",
    settings: null
  },
  getPreferences() {
    return this.profile.settings?.theme || "default";
  }
};

const admin = {
  profile: {
    name: "Admin"
  },
  getPreferences() {
    return this.profile.settings?.theme || "default";
  }
};

console.log(user.getPreferences());
console.log(admin.getPreferences());
console.log(user.profile.extra?.id?.toString());

var a=[1,2,3,4,5];
console.log(a.some(x=>x>4)); 
console.log(a.some(x=>x>5));

const user = {
  profile: {
    getName: () => "Marcus",
    getAge: () => 30,
  },
  settings: null,
};

const name = user.profile?.getName?.();
const age = user.profile?.getAge?.();
const theme = user.settings?.getTheme?.() ?? "dark";
const lang = user.address?.getLocale?.() ?? "en-US";

console.log(`${name} | ${age} | ${theme} | ${lang}`);

const inventory = {
  items: ['apple', 'banana', 'orange'],
  [Symbol.iterator]: function() {
    let index = 0;
    const items = this.items;
    
    return {
      next: function() {
        return index < items.length ?
          { value: items[index++].toUpperCase(), done: false } :
          { done: true };
      }
    };
  }
};

const result = [...inventory].join(' + ');
console.log(result);

const target = { name: 'Maya', age: 25 };
const handler = {
  get(obj, prop) {
    if (prop in obj) {
      return obj[prop];
    }
    return `Property '${prop}' not found`;
  },
  set(obj, prop, value) {
    if (typeof value === 'string') {
      obj[prop] = value.toUpperCase();
    } else {
      obj[prop] = value;
    }
    return true;
  }
};
const proxy = new Proxy(target, handler);
proxy.city = 'tokyo';
console.log(proxy.name);
console.log(proxy.city);
console.log(proxy.country);

const obj = { a: 1, b: { c: 2 } };
const frozen = Object.freeze(obj);
frozen.a = 99;
frozen.b.c = 88;
frozen.d = 77;

const sealed = Object.seal({ x: 10, y: 20 });
sealed.x = 30;
sealed.z = 40;
delete sealed.y;

console.log(obj.a, obj.b.c, obj.d);
console.log(sealed.x, sealed.y, sealed.z);

const num = 10;
const add = () => {
   console.log(num + num);
};

(function () {
   const num = 5;
   add();
})();

class CustomError extends Error {
  constructor(message) {
    super(message);
    this.name = 'CustomError';
  }
}

try {
  try {
    throw new CustomError('inner error');
  } catch (e) {
    console.log(e.name);
    throw new Error('outer error');
  }
} catch (e) {
  console.log(e.message);
  console.log(e instanceof CustomError);
}

var s="100001,111,12222221,222,3333,12321,14441";

var match1=s.match(/1.*1/g)
var match2=s.match(/1.+1/g)

console.log(match1)  
console.log(match2)

const str = "a 1 b 2 c 3 d 04";

function foo(str) {
   const regex = /\d+/g;
   const matches = str.match(regex);
   return matches.lenght;
}

const promise1 = Promise.resolve('first');
const promise2 = new Promise(resolve => {
  resolve('second');
});

const promise3 = Promise.resolve().then(() => 'third');

async function test() {
  console.log('start');
  
  const result1 = await promise1;
  console.log(result1);
  
  const result2 = await promise2;
  console.log(result2);
  
  const result3 = await promise3;
  console.log(result3);
  
  console.log('end');
}

test();

function* range(start, end) {
  let current = start;
  while (current <= end) {
    if (current % 3 === 0) {
      current++;
      continue;
    }
    yield current++;
  }
}

const gen = range(4, 10);
const result = [...gen];
console.log(result);

const num = 10;
const add = () => {
   console.log(num + num);
};

(function () {
   const num = 5;
   add();
})();

const obj = {};
const sym1 = Symbol('description');
const sym2 = Symbol('description');

obj[sym1] = 'Value 1';
obj[sym2] = 'Value 2';
obj.regularProp = 'Regular';

const allKeys = Object.getOwnPropertySymbols(obj).length + Object.keys(obj).length;
const comparison = sym1 === sym2;

console.log(allKeys + ',' + comparison);

function* range(start, end) {
  let current = start;
  while (current <= end) {
    if (current % 3 === 0) {
      current++;
      continue;
    }
    yield current++;
  }
}

const gen = range(4, 10);
const result = [...gen];
console.log(result);

function delayedLog(item) {
  setTimeout(() => {
    console.log(item);
  }, 1000);
}
for (var i = 0; i < 3; i++) {
  delayedLog(i);
}

class Rectangle {
  constructor(width, height) {
    this.width = width;
    this.height = height;
  }

  get area() {
    return this.width * this.height;
  }
}

const rectangle = new Rectangle(5, 10);
console.log(rectangle.area());

const config = {
  port: 0,
  timeout: null,
  retries: '',
  cache: false,
  debug: undefined
};

const port = config.port ?? 3000;
const timeout = config.timeout ?? 5000;
const retries = config.retries ?? 3;
const cache = config.cache ?? true;
const debug = config.debug ?? false;

console.log([port, timeout, retries, cache, debug]);

const person = {
  name: 'Alice',
  age: 25,
  city: 'Wonderland'
};

const additionalInfo = {
  age: 30,
  occupation: 'Explorer'
};

const combined = {
  ...person,
  ...additionalInfo
};

console.log(combined.age);

const inventory = {
  items: ['apple', 'banana', 'orange'],
  [Symbol.iterator]: function() {
    let index = 0;
    const items = this.items;
    
    return {
      next: function() {
        return index < items.length ?
          { value: items[index++].toUpperCase(), done: false } :
          { done: true };
      }
    };
  }
};

const result = [...inventory].join(' + ');
console.log(result);