function greet(name) {
  return `Hello, ${name}!`;
}

function highlight(strings, ...values) {
  return strings.reduce((result, str, i) => {
    return result + str + (values[i] ? `<em>${values[i]}</em>` : '');
  }, '');
}

const user = 'Sarah';
const status = 'online';

console.log(highlight`User ${user} is currently ${status}.`);

async function foo() {
  console.log('Start');
  await Promise.resolve().then(() => {
    console.log('Inside Promise');
  });
  console.log('End');
}

foo();
console.log('Outside');

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 result = (function() {
  let count = 0;
  
  return {
    increment() {
      return ++count;
    },
    get value() {
      return count;
    },
    reset() {
      const oldCount = count;
      count = 0;
      return oldCount;
    }
  };
})();

result.increment();
result.increment();
console.log(result.reset() + result.value + result.increment());

const user = {
  profile: {
    settings: {
      theme: 'dark'
    }
  }
};

const getTheme = (obj) => obj?.profile?.settings?.theme ?? 'light';
const getLanguage = (obj) => obj?.profile?.settings?.language ?? 'en';
const getNotifications = (obj) => obj?.profile?.notifications?.enabled ?? true;

console.log(getTheme(user));
console.log(getLanguage(user));
console.log(getNotifications(user));
console.log(getTheme(null));

let obj = { a: 1 };
let proto = { b: 2 };

Object.setPrototypeOf(obj, proto);

for (let key in obj) {
  console.log(key);
}

const weakMap = new WeakMap();
const array = [{}, {}];

array.forEach(obj => weakMap.set(obj, obj));
const result = array.map(obj => weakMap.get(obj) === obj);

console.log(result);

const team = {
  members: ['Alice', 'Bob', 'Charlie'],
  [Symbol.iterator]: function*() {
    let index = 0;
    while(index < this.members.length) {
      yield this.members[index++].toUpperCase();
    }
  }
};

const result = [];
for (const member of team) {
  result.push(member);
}

console.log(result.join('-'));

var str="My name is John";
var words1=str.split(" ",3);
console.log("words1:",words1);
var words2=str.split(" ",5);
console.log("words2:",words2);

function createCounter() {
  let count = 0;
  return {
    increment: () => ++count,
    decrement: () => --count,
    getValue: () => count
  };
}

const counter1 = createCounter();
const counter2 = createCounter();
counter1.increment();
counter1.increment();
counter2.increment();
console.log(counter1.getValue(), counter2.getValue());
counter1.decrement();
console.log(counter1.getValue(), counter2.getValue());

const wm = new WeakMap();
const obj1 = { name: 'first' };
const obj2 = { name: 'second' };
const obj3 = obj1;

wm.set(obj1, 'value1');
wm.set(obj2, 'value2');
wm.set(obj3, 'value3');

console.log(wm.get(obj1));
console.log(wm.get(obj2));
console.log(wm.get(obj3));
console.log(wm.has(obj1));
console.log(wm.size);

const user = {
  profile: {
    name: 'Alice',
    settings: {
      notifications: {
        email: true,
        sms: false
      }
    }
  },
  getPreference(type) {
    return this.profile?.settings?.notifications?.[type] ?? 'not configured';
  }
};

const admin = {
  profile: {
    name: 'Admin',
    settings: null
  },
  getPreference: user.getPreference
};

console.log(admin.getPreference('email'));

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

try {
  throw new CustomError('Something went wrong');
} catch (e) {
  console.log(e instanceof Error);
  console.log(e instanceof CustomError);
  console.log(e.constructor.name);
  console.log(e.name);
}

const regex = /a/g;
const str = 'banana';
console.log(str.match(regex));

var arr=[1,2,3,4,5];
console.log(arr.map((prev,curr)=>prev+curr));
console.log(arr.reduce((a,b)=>a+b));
console.log(arr.filter((a,b)=> (a + b) <= 5));

const obj = {};
let value = 0;

Object.defineProperty(obj, 'prop', {
  get() {
    return value;
  },
  set(newValue) {
    value = newValue + 1;
  },
  configurable: true,
  enumerable: true
});

obj.prop = 10;
console.log(obj.prop);

const a = async () => {
   return Promise.reject('rejected');
};

a().catch(error => console.log(error));
console.log('done');

const obj = { count: 0 };
const arr = [obj, obj, obj];

function increment(item) {
  item.count++;
  return item;
}

const results = arr.map(increment);
console.log(obj.count);
console.log(results[0] === results[1]);
console.log(results.length);
console.log(arr[0].count);

function createCounter() {
  let count = 0;
  
  function increment() {
    count++;
    return count;
  }
  
  function decrement() {
    count--;
    return count;
  }
  
  return { increment, decrement, reset: () => count = 0 };
}

const counter = createCounter();
counter.increment();
counter.increment();
counter.decrement();

const { increment, reset } = counter;
increment();
reset();
increment();

console.log(counter.increment());

const map = new WeakMap();

let obj1 = { name: 'user1' };
let obj2 = { name: 'user2' };

map.set(obj1, 'data for user1');
map.set(obj2, 'data for user2');

console.log(map.has(obj1));
obj1 = null;

console.log(map.has(obj1));
console.log(map.get(obj2));

console.log('1');
setTimeout(() => console.log('2'), 0);
Promise.resolve().then(() => console.log('3'));
setTimeout(() => console.log('4'), 0);
console.log('5');
Promise.resolve().then(() => {
  console.log('6');
  return Promise.resolve();
}).then(() => console.log('7'));
queueMicrotask(() => console.log('8'));
console.log('9');