Generic types for flexibility

An API that returns Promise<any> for network requests or data operations forces every TypeScript consumer to cast results manually — const users = await client.get('/users') as User[]. This eliminates compile-time type checking at exactly the boundary where runtime errors are most common. ISO 25010 modifiability suffers because any change to the response shape goes undetected until runtime. The consumer cannot trust the type system to catch contract mismatches between their models and your API's actual output.

Add generic type parameters to data-handling methods so consumers can specify their expected response types.

// Before — returns any:
export class Client {
  async request(path: string): Promise<any> { /* ... */ }
}

// After — generic return type:
export class Client {
  async request<T>(path: string): Promise<T> { /* ... */ }
}

// Consumer gets full type safety:
const users = await client.request<User[]>('/api/users')
//    ^? User[]

For event emitters, use a typed event map: on<K extends keyof Events>(event: K, handler: (data: Events[K]) => void). At least 50% of data-handling APIs should use generics before this check passes.