JavaScript test

const x = [1, 2, 3, 4, 5];
console.log(x.slice(1, 3));

class Counter {
  constructor(max) {
    this.max = max;
  }
  
  *[Symbol.iterator]() {
    let current = 0;
    while (current < this.max) {
      yield current++;
    }
  }
}

const counter = new Counter(3);
const result = [...counter, ...counter];
console.log(result);

const numbers = [1, 2, 3];
numbers.push(4);
console.log(numbers);

var a=[1,2,3,4,5];
a.every(x=>{
  console.log(x); 
  return x<4;
})

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 target = { name: 'Sarah', age: 25 };

const handler = {
  get(obj, prop) {
    if (prop in obj) {
      return obj[prop];
    }
    return `Property '${prop}' not found`;
  },
  set(obj, prop, value) {
    obj[prop] = value.toString().toUpperCase();
    return true;
  }
};

const proxy = new Proxy(target, handler);
proxy.city = 'boston';
console.log(proxy.name);
console.log(proxy.city);
console.log(proxy.country);

const obj = { a: 1, b: 2 };
const proxy = new Proxy(obj, {
  get(target, prop) {
    return prop in target ? target[prop] : 0;
  }
});

console.log(proxy.a, proxy.b, proxy.c);

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;
}

class Logger {
  constructor(prefix) {
    this.prefix = prefix;
  }
  log(message) {
    console.log(`${this.prefix}: ${message}`);
  }
}

class Database {
  constructor(logger) {
    this.logger = logger;
  }
  save(data) {
    this.logger.log(`Saving ${data}`);
    return `${data}_saved`;
  }
}

const logger = new Logger('DB');
const db = new Database(logger);
const result = db.save('user');
console.log(result);

console.log(2 + 2 % 3);

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

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

setTimeout(() => console.log('Timeout 1'), 100);

setTimeout(() => {
  console.log('Timeout 2');
  Promise.resolve().then(() => console.log('Promise in Timeout 2'));
}, 50);

Promise.resolve().then(() => console.log('Promise 1'));

setTimeout(() => console.log('Timeout 3'), 150);

console.log('Sync');

const num = 9;
const str = num.toString().padStart(3, "0");
console.log(str);

const obj = {
  value: 1,
  increment() {
    this.value++;
  }
};

const increment = obj.increment;
increment();

console.log(obj.value);

function getItems(fruitList, ...args, favoriteFruit) {
   return [...fruitList, ...args, favoriteFruit]
}

getItems(["banana", "apple"], "pear", "orange")

console.log('Start');

setTimeout(() => {
  console.log('Timeout 1');
}, 0);

Promise.resolve().then(() => {
  console.log('Promise 1');
}).then(() => {
  console.log('Promise 2');
});

setTimeout(() => {
  console.log('Timeout 2');
}, 0);

console.log('End');

const obj = {
  a: 1,
  then(resolve) {
    resolve(this.a);
  }
};

obj.then(console.log);

class VideoCall {
  constructor() {
    this.pc = { iceConnectionState: 'new' };
    this.streams = [];
  }
  
  async connect() {
    this.pc.iceConnectionState = 'checking';
    await Promise.resolve();
    this.pc.iceConnectionState = 'connected';
    this.streams.push('remote-video');
    return this.pc.iceConnectionState;
  }
  
  handleConnectionChange() {
    const states = ['new', 'checking', 'connected'];
    return states.map(state => {
      return this.pc.iceConnectionState === state ? `Status: ${state}` : null;
    }).filter(Boolean);
  }
}

const call = new VideoCall();
call.connect().then(() => {
  console.log(call.handleConnectionChange());
});

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 weakMap = new WeakMap();
const obj1 = {};
const obj2 = { key: 'value' };

weakMap.set(obj1, obj2);

const result = weakMap.get(obj1).key.split('').reverse().join('');

console.log(result);