function outer() {
  let x = 10;
  
  function inner() {
    console.log(x);
    
    if(true) {
      let x = 20;
      console.log(x);
    }
    
    console.log(x);
  }
  
  inner();
}

outer();

const ws = new WeakSet();
const obj1 = { id: 1 };
const obj2 = { id: 2 };

ws.add(obj1);
ws.add(obj2);
ws.delete(obj1);

const obj3 = { id: 2 };

console.log([
  ws.has(obj2),
  ws.has(obj1),
  ws.has(obj3),
  ws.has({ id: 2 })
]);

class Task {
  constructor(name) {
    this.name = name;
  }
  async execute() {
    const result = await Promise.resolve(this.name);
    return { result };
  }
}

const task = new Task('test');
task.execute().then(console.log);

const users = [
  { id: 1, name: 'Alice', age: 25 },
  { id: 2, name: 'Bob', age: 30 },
  { id: 3, name: 'Charlie', age: 35 }
];

const result = users
  .filter(user => user.age > 25)
  .map(user => user.name.toUpperCase())
  .reduce((acc, name) => acc + name[0], '');

console.log(result);

async function getData() {
  return Promise.resolve(1);
}

async function process() {
  try {
    const x = await getData();
    const y = await Promise.resolve(x + 1);
    console.log(y + await Promise.resolve(1));
  } catch(err) {
    console.log('Error');
  }
}

process();

const cache = new WeakMap();
const obj1 = { id: 1 };
const obj2 = { id: 2 };

cache.set(obj1, 'data1');
cache.set(obj2, 'data2');

obj2.newProp = 'test';

console.log(cache.has(obj1), cache.has(obj2), cache.has({ id: 1 }));

const counter = {
  count: 0,
  increment() {
    this.count++;
    return this.count;
  }
};

const inc = counter.increment;
const boundInc = counter.increment.bind(counter);

console.log([
  counter.increment(),
  inc(),
  boundInc(),
  counter.count
]);