Domain-Driven Design with TypeScript

Domain-Driven Design (DDD) provides a powerful framework for tackling complex software projects by focusing on the core domain and domain logic. When combined with TypeScript's robust type system, DDD becomes even more effective at creating maintainable, scalable applications. Let's explore how to implement these principles in modern TypeScript applications.

Understanding Core DDD Concepts

Before diving into implementation, let's understand the key concepts that form the foundation of DDD:

Ubiquitous Language

A shared language between developers and domain experts that's reflected in your code.

// Instead of generic terms like "user" and "item"
interface Customer {
  customerId: CustomerId;
  name: string;
  membershipTier: MembershipTier;
  placeOrder(items: Product[]): Order;
}

// Using domain-specific value objects
type CustomerId = string & { readonly _brand: unique symbol };
type MembershipTier = "STANDARD" | "PREMIUM" | "EXECUTIVE";