TypeScript e’lonlarni birlashtirish

Deklaratsiyani birlashtirishni tushunish

Deklaratsiyani birlashtirish bir xil nomdagi bir nechta deklaratsiyalarni bitta ta’rifga birlashtirish imkonini beruvchi kuchli TypeScript xususiyatidir.

Bu sizga murakkab turlarni bosqichma-bosqich yaratish va mavjud turlarni xavfsiz tarzda kengaytirish imkonini beradi.

Asosiy afzalliklari

Progressive Enhancement : Turlarni bir nechta deklaratsiyalar bo‘yicha bosqichma-bosqich yarating
Extensibility : Asl ta’riflarni o‘zgartirmasdan mavjud turlarga yangi a’zolarni qo‘shing
Organization : Katta turdagi ta’riflarni mantiqiy guruhlarga bo‘ling
Compatibility : Zarur bo‘lganda, uchinchi tomon turi ta’riflarini kengaytiring

Umumiy foydalanish holatlari

O‘rnatilgan turlari va uchinchi tomon kutubxonalari turlarini kengaytirish
JavaScript kutubxonalari uchun turdagi ma’lumotlarni qo‘shish
Bir nechta fayllar bo‘ylab katta interfeyslarni tashkil qilish
Usul zanjiri bilan ravon API yaratish
Modulni kengaytirish naqshini amalga oshirish

Interfeysni birlashtirish

Xuddi shu nomdagi interfacelar avtomatik ravishda birlashtiriladi:

Misol

// First declaration
interface Person {
  name: string;
  age: number;
}

// Second declaration with the same name
interface Person {
  address: string;
  email: string;
}

// TypeScript merges them into:
// interface Person {
// name: string;
// age: number;
// address: string;
// email: string;
// }

const person: Person = {
  name: "John",
  age: 30,
  address: "123 Main St",
  email: "john@example.com"
};

console.log(person);

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Birlashtirish bilan funksiyaning haddan tashqari yuklanishi

Amalga oshirilganda keyin birlashtiriladigan bir nechta funksiya deklaratsiyasini belgilashingiz mumkin:

Misol

// Function overloads
function processValue(value: string): string;
function processValue(value: number): number;
function processValue(value: boolean): boolean;

// Implementation that handles all overloads
function processValue(value: string | number | boolean): string | number | boolean {
  if (typeof value === "string") {
    return value.toUpperCase();
  } else if (typeof value === "number") {
    return value * 2;
  } else {
    return !value;
  }
}

// Using the function with different types
console.log(processValue("hello")); // "HELLO"
console.log(processValue(10)); // 20
console.log(processValue(true)); // false

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Nom maydonini birlashtirish

Xuddi shu nomdagi nomlar birlashtiriladi:

Misol

namespace Validation {
  export interface StringValidator {
    isValid(s: string): boolean;
  }
}

namespace Validation {
  export interface NumberValidator {
    isValid(n: number): boolean;
  }

  export class ZipCodeValidator implements StringValidator {
    isValid(s: string): boolean {
      return s.length === 5 && /^\d+$/.test(s);
    }
  }
}

// After merging:
// namespace Validation {
// export interface StringValidator { isValid(s: string): boolean; }
// export interface NumberValidator { isValid(n: number): boolean; }
// export class ZipCodeValidator implements StringValidator { ... }
// }

// Using the merged namespace
const zipValidator = new Validation.ZipCodeValidator();

console.log(zipValidator.isValid("12345")); // true
console.log(zipValidator.isValid("1234")); // false
console.log(zipValidator.isValid("abcde")); // false

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Class va interfeysni birlashtirish

Class deklaratsiyasi bir xil nomdagi interface bilan birlashishi mumkin:

Misol

// Interface declaration
interface Cart {
  calculateTotal(): number;
}

// Class declaration with same name
class Cart {
  items: { name: string; price: number }[] = [];

  addItem(name: string, price: number): void {
    this.items.push({ name, price });
  }

   // Must implement the interface method
   calculateTotal(): number {
    return this.items.reduce((sum, item) => sum + item.price, 0);
  }
}

// Using the merged class and interface
const cart = new Cart();
cart.addItem("Book", 15.99);
cart.addItem("Coffee Mug", 8.99);

console.log(`Total: $${cart.calculateTotal().toFixed(2)}`);

Raqamlarni birlashtirish

Xuddi shu nomdagi enum deklaratsiyasi birlashtiriladi:

Misol

// First part of the enum
enum Direction {
  North,
  South
}

// Second part of the enum
enum Direction {
  East = 2,
  West = 3
}

// After merging:
// enum Direction {
// North = 0,
// South = 1,
// East = 2,
// West = 3
// }

console.log(Direction.North); // 0
console.log(Direction.South); // 1
console.log(Direction.East); // 2
console.log(Direction.West); // 3

// Can also access by value
console.log(Direction[0]); // "North"
console.log(Direction[2]); // "East"

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Modulni kengaytirish

Mavjud modullar yoki kutubxonalarni qo‘shimcha turlar va funksiyalarni e’lon qilish orqali kengaytirishingiz mumkin:

Misol

// Original library definition
// Imagine this comes from a third-party library
declare namespace LibraryModule {
  export interface User {
    id: number;
    name: string;
  }
  export function getUser(id: number): User;
}

// Augmenting with additional functionality (your code)
declare namespace LibraryModule {
  // Add new interface
  export interface UserPreferences {
    theme: string;
    notifications: boolean;
  }

  // Add new property to existing interface
  export interface User {
    preferences?: UserPreferences;
  }

  // Add new function
  export function getUserPreferences(userId: number): UserPreferences;
}

// Using the augmented module
const user = LibraryModule.getUser(123);
console.log(user.preferences?.theme);

const prefs = LibraryModule.getUserPreferences(123);
console.log(prefs.notifications);

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Eng yaxshi amaliyotlar

Deklaratsiyani birlashtirishdan foydalanishda e’tiborga olish kerak bo‘lgan ba’zi qoidalar mavjud:

Order matters for function overloads : Amalga oshirish imzosi eng umumiy bo‘lishi kerak
Non-function members must be compatible : Agar ikkita interface bir xil nomdagi xususiyatni e’lon qilsa, turlar bir xil yoki mos bo‘lishi kerak
Later interfaces take precedence : Agar birlashtirilgan interfeyslarda ziddiyatlar mavjud bo‘lsa, oxirgi deklaratsiya g‘alaba qozonadi
Private and protected members : Agar classlar bir xil nomli, lekin har xil turdagi shaxsiy yoki himoyalangan a’zolarga ega bo‘lsa, ularni birlashtirib bo‘lmaydi.
Namespace exports : Birlashtirilgandan keyin faqat eksport qilingan deklaratsiyalar nom maydonidan tashqarida ko‘rinadi

Ishlash bo‘yicha mulohazalar

Compilation Time : Haddan tashqari deklaratsiyani birlashtirish kompilyatsiya vaqtini oshirishi mumkin
Type Checking : Birlashtirilgan murakkab turlar IDE ishlashiga ta’sir qilishi mumkin
Bundle Size : Deklaratsiyani birlashtirish ish vaqti unumdorligiga yoki to‘plam hajmiga ta’sir qilmaydi

Optimallashtirish bo‘yicha maslahatlar:

Birlashtirilgan interfeyslarni diqqat markazida va yaxlit holda saqlang
Birlashtirilgan turlarda chuqur joylashishdan saqlaning
Birlashtirish o‘rniga oddiy turdagi kombinatsiyalar uchun type taxalluslaridan foydalaning

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