Angular — TypeScript

Interfaces

interface User {
  id: number;
  name: string;
  email: string;
  age?: number;  // Optional
}

function greet(user: User): string {
  return `Hello, ${user.name}!`;
}

Types

type Status = 'active' | 'inactive' | 'pending';
type ID = string | number;

const status: Status = 'active';

Generics

class DataStore<T> {
  private items: T[] = [];
  
  add(item: T) {
    this.items.push(item);
  }
  
  getAll(): T[] {
    return this.items;
  }
}

const userStore = new DataStore<User>();

Decorators

function Log(target: any, key: string, descriptor: PropertyDescriptor) {
  const original = descriptor.value;
  descriptor.value = function(...args: any[]) {
    console.log(`Calling ${key}`);
    return original.apply(this, args);
  };
}

class Calculator {
  @Log
  add(a: number, b: number) {
    return a + b;
  }
}

Utility Types

interface User {
  id: number;
  name: string;
  email: string;
}

Partial<User>     // All optional
Required<User>    // All required
Pick<User, 'id'>  // Only id
Omit<User, 'id'>  // Without id

Mini Practice

1. Define interfaces
2. Use type unions
3. Create generic classes
4. Use utility types

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Continue with Security — Angular security best practices.