typescript-implementation

# TypeScript Implementation Skill

## Quick Start

### Basic Types
```typescript
// Primitive types
let name: string = "Angular";
let version: number = 18;
let active: boolean = true;

// Union types
let id: string | number;

// Type aliases
type User = {
  name: string;
  age: number;
};
```

### Interfaces and Generics
```typescript
interface Component {
  render(): string;
}

// Generic interface
interface Repository<T> {
  getAll(): T[];
  getById(id: number): T | undefined;
}

class UserRepository implements Repository<User> {
  getAll(): User[] { /* ... */ }
  getById(id: number): User | undefined { /* ... */ }
}
```

### Decorators (Essential for Angular)
```typescript
// Class decorator
function Component(config: any) {
  return function(target: any) {
    target.prototype.selector = config.selector;
  };
}

// Method decorator
function Log(target: any, propertyKey: string, descriptor: PropertyDescriptor) {
  const originalMethod = descriptor.value;
  descriptor.value = function(...args: any[]) {
    console.log(`Calling ${propertyKey} with:`, args);
    return originalMethod.apply(this, args);
  };
  return descriptor;
}

// Parameter decorator
function Required(target: any, propertyKey: string, parameterIndex: number) {
  // Validation logic
}
```

## Essential Concepts

### Advanced Types

**Utility Types:**
- `Partial<T>` - Make all properties optional
- `Required<T>` - Make all properties required
- `Readonly<T>` - Make all properties readonly
- `Record<K, T>` - Object with specific key types
- `Pick<T, K>` - Select specific properties
- `Omit<T, K>` - Exclude specific properties

**Conditional Types:**
```typescript
type IsString<T> = T extends string ? true : false;
type A = IsString<"hello">; // true
type B = IsString<number>; // false
```

**Mapped Types:**
```typescript
type Getters<T> = {
  [K in keyof T as `get${Capitalize<string & K>}`]: () => T[K];
};
```

### Generic Constraints
```typescript
// Extend constraint
function processUser<T extends