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TypeScript Patterns for Large Codebases: Generics, Discriminated Unions & Module Boundaries

The TypeScript patterns that keep large codebases maintainable — discriminated unions for state machines, branded types for domain safety, and module boundary patterns that prevent spaghetti imports.

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12 min read
Written by
Rakesh · DEVMANUSH RAKY
TypeScript Patterns for Large Codebases: Generics, Discriminated Unions & Module Boundaries

TypeScript has become the industry standard for scalable JS apps. Understanding high-level patterns like Generics and Utility Types is key to building durable systems.

The Power of Generics

Generics allow you to create components and functions that work over a variety of types rather than a single one. This leads to much more reusable and type-safe utilities.

interface ApiResponse<T> {
  data: T;
  error: string | null;
}

// Usage with a specific user type
const response: ApiResponse<User> = await fetchUser();

Mapped and Conditional Types

Advanced features like 'Partial', 'Pick', and conditional types allow you to transform existing types into new ones, maintaining a single source of truth for your data models.

  • TypeScript
  • JavaScript
  • Architecture
  • Best Practices
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