JavaScript prototip va meros zanjiri

Klasslar darsida metodlar bir joyda saqlanishini ko’rgan edik. Endi shu mexanizmning o’ziga qaraymiz — u JavaScript’ni boshqa tillardan ajratib turadi.

Xossa qayerdan topiladi

JavaScript

const talaba = { ism: "Aziz" };

console.log(talaba.ism);
console.log(talaba.toString);
console.log(talaba.hasOwnProperty("ism"));

toString va hasOwnProperty ni biz yozmadik, lekin ular bor. Chunki obyekt xossani o’zida topa olmasa, prototipiga qaraydi.

Zanjirni ko’rish

JavaScript

const talaba = { ism: "Aziz" };

const p1 = Object.getPrototypeOf(talaba);
console.log("1-daraja:", p1 === Object.prototype);

const p2 = Object.getPrototypeOf(p1);
console.log("2-daraja:", p2);

console.log("O'ziniki:", Object.keys(talaba));

Zanjir null bilan tugaydi — bu izlashning oxiri.

Massivning zanjiri

JavaScript

const massiv = [1, 2, 3];

console.log(Object.getPrototypeOf(massiv) === Array.prototype);
console.log(Object.getPrototypeOf(Array.prototype) === Object.prototype);

console.log(massiv.map === Array.prototype.map);

map massivning o’zida emas — Array.prototype da. Barcha massivlar shu bitta funksiyani baham ko’radi.

Object.create — prototipni qo’lda belgilash

JavaScript

const hayvon = {
ovoz() {
  return this.nom + " ovoz chiqardi";
},
};

const it = Object.create(hayvon);
it.nom = "Sherbek";

console.log(it.ovoz());
console.log(Object.keys(it));
console.log(Object.getPrototypeOf(it) === hayvon);

it da faqat nom bor, ovoz esa prototipdan olindi.

Prototipni o’zgartirish — zanjir jonli

JavaScript

const asos = { salom() { return "Salom"; } };
const obyekt = Object.create(asos);

console.log(obyekt.salom());

asos.xayr = function () { return "Xayr"; };

console.log(obyekt.xayr());

xayr obyekt yaratilgandan keyin qo’shildi, lekin baribir ko’rindi — zanjir nusxa emas, jonli bog’lanish.

Xossa berish — zanjirga tegmaydi

JavaScript

const asos = { qiymat: "asosdan" };
const obyekt = Object.create(asos);

console.log(obyekt.qiymat);

obyekt.qiymat = "o'ziniki";

console.log(obyekt.qiymat);
console.log(asos.qiymat);

delete obyekt.qiymat;
console.log(obyekt.qiymat);

O’zlashtirish har doim obyektning o’zida yangi xossa yaratadi. Prototipdagi qiymat “to’siladi”, lekin o’zgarmaydi — o’chirilganda yana ko’rinadi.

O’ziniki yoki merosmi

JavaScript

const asos = { a: 1 };
const obyekt = Object.create(asos);
obyekt.b = 2;

console.log("a bormi:", "a" in obyekt);
console.log("a o'zinikimi:", Object.hasOwn(obyekt, "a"));
console.log("b o'zinikimi:", Object.hasOwn(obyekt, "b"));

for (const kalit in obyekt) {
console.log("for...in:", kalit);
}

console.log("Object.keys:", Object.keys(obyekt));

Farq muhim: in va for...in zanjirni ham ko’radi, Object.keys va Object.hasOwn — faqat obyektning o’zini.

Klass — prototip ustidagi qobiq

Klass yozuvi yangi mexanizm emas, mavjudining qulay shakli:

JavaScript

class Talaba {
constructor(ism) {
  this.ism = ism;
}
salom() {
  return "Salom, " + this.ism;
}
}

const t = new Talaba("Aziz");

console.log(Object.keys(t));
console.log(Object.getPrototypeOf(t) === Talaba.prototype);
console.log(typeof Talaba.prototype.salom);
console.log(t.salom === Talaba.prototype.salom);

Ko’rinib turibdi: ism obyektda, salom esa Talaba.prototype da.

Konstruktor funksiya — eski uslub

Klasslardan oldin shunday yozilardi:

JavaScript

function Talaba(ism) {
this.ism = ism;
}

Talaba.prototype.salom = function () {
return "Salom, " + this.ism;
};

const t = new Talaba("Aziz");
console.log(t.salom());
console.log(t instanceof Talaba);

Natija klass bilan bir xil. Eski kodni o’qishda bu shakl uchraydi.

Meros zanjiri

JavaScript

class Inson {
nafas() { return "nafas olmoqda"; }
}

class Talaba extends Inson {
oqiydi() { return "o'qimoqda"; }
}

const t = new Talaba();

console.log(t.oqiydi());
console.log(t.nafas());

let daraja = Object.getPrototypeOf(t);
let n = 1;
while (daraja) {
console.log(n + "-daraja:", daraja.constructor.name);
daraja = Object.getPrototypeOf(daraja);
n++;
}

Zanjir: t → Talaba.prototype → Inson.prototype → Object.prototype → null. Meros shu zanjirni quradi.

Prototipsiz obyekt

JavaScript

const toza = Object.create(null);
toza.ism = "Aziz";

console.log(toza.ism);
console.log(toza.toString);
console.log(Object.getPrototypeOf(toza));

Zanjirsiz obyekt — sof lug’at. Kalitlar toString kabi merosiy nomlar bilan to’qnashmaydi.

Amaliy mashq

Obyekt yaratib, Object.getPrototypeOf bilan zanjirni ko’ring;
Object.create bilan prototipli obyekt yasang;
prototipga metod qo’shib, mavjud obyektda ko’ringanini tasdiqlang;
prototipdagi xossani obyektda “to’sib”, keyin delete qiling;
in, Object.hasOwn va Object.keys natijasini solishtiring;
klass yozib, metod prototype da ekanini tekshiring.

Qisqacha xulosa

Har obyekt prototip bilan bog’langan; xossa u yerdan izlanadi.
Zanjir null bilan tugaydi.
Object.create(asos) prototipni qo’lda belgilaydi.
O’zlashtirish doim obyektning o’zida yangi xossa yaratadi.
in/for...in zanjirni ko’radi; Object.keys/hasOwn — faqat o’zini.
Klass — prototip mexanizmi ustidagi qulay yozuv.

Keyingi darsda event loop — JavaScript navbat tizimi.