let set = new Set();

let john = { name: "John" };
let pete = { name: "Pete" };
let mary = { name: "Mary" };

// visits, some users come multiple times
set.add(john);
set.add(pete);
set.add(mary);
set.add(john);
set.add(mary);

// set keeps only unique values
alert( set.size ); // 3

for (let user of set) {
  alert(user.name); // John (then Pete and Mary)
}

let user = {
  name: "John",
  age: 30,

  toString() {
    return `{name: "${this.name}", age: ${this.age}}`;
  }
};

alert(user); // {name: "John", age: 30}

let student = {
  name: 'John',
  age: 30,
  isAdmin: false,
  courses: ['html', 'css', 'js'],
  spouse: null
};

let json = JSON.stringify(student);


console.log(student)

alert( Math.max(3, 5, 1) ); // 5

JavaScript-da rest operatori (...) vazifasi
Rest operatori (...) bir nechta argument yoki massiv elementlarini bitta o‘zgaruvchiga yig‘ish uchun ishlatiladi. U asosan funksiya argumentlarini yoki massiv va obyektlardan ma'lumot olish uchun ishlatiladi.

function logger(a, b, ...rest) {
  console.log(a);
  console.log(b);
  console.log(rest);
}
logger(12, 10, 1, 2, 3, 4, 5, 6);

a = 12

b = 10

...rest = [1, 2, 3, 4, 5, 6]

Rest operatori (...rest) barcha ortiqcha argumentlarni massiv sifatida saqlaydi.

Logger funksiyasiga nechta argument bersangiz ham, a va b birinchi ikkita qiymatni oladi, qolganlari rest massiviga tushadi.

const cards = document.querySelectorAll(".catalog_box"),
textInfo = document.querySelector(".text");

cards.forEach(card => {
  card.addEventListener("mousemove", (e) => {
    let half = card.clientWidth / 2
    let x = e.offsetX - half 
    let y = e.offsetY - half
    textInfo.innerHTML = `${x}px | ${y}px`
    card.style.transform = `rotateY(${x/4}deg) rotateX(${-y/4}deg)`
  })
  card.onmouseout = () => card.style.transform = `rotate(0)`
})

//ORIENTED OPERATING PROGRAMMING

class Typing {
  constructor({el, interval, delay}){
    this.el = document.querySelector(el);
    this.interval = interval || 500 
    this.delay = delay == undefined ? 1000 : delay
    this.text = this.el.innerHTML.trim()
    this.el.innerHTML = ""
    setTimeout(() => this.write(i), this.delay);  
  }
  write(i = 0){
    this.el.innerHTML += this.text[i] 
    i++;
    if (i < this.text.length) {
      setTimeout(() => this.write(i), this.interval);      
    }

  }
}
new Typing({
    el: ".header__content h1" ,
    interval: 300,
    delay:1000
});

DOM

document.body.style.background = 'red'; // make the background red

setTimeout(() => document.body.style.background = '', 3000); // return back

const element = document.getElementById('myElement');
console.log(element.clientWidth);  // Elementning ko'rinadigan kengligi
console.log(element.clientHeight); // Elementning ko'rinadigan balandligi

let hour = 12;
let minute = 30;

if (hour == 12 && minute == 30) {
  alert( 'The time is 12:30' );
}