Stop TypeScript Chaos: Master Interfaces and Types for Bulletproof Code

You're tired of wrestling with TypeScript's type system instead of building features. Your interfaces are inconsistent, your types are scattered across files, and every code review turns into a debate about interface vs type. Here's how to end the confusion and build TypeScript code that actually makes development faster.

The Real Problem: TypeScript Complexity is Killing Your Velocity

Modern web development demands type safety, but most teams struggle with:

Interface vs type confusion - Using the wrong construct for the job, leading to compilation errors and maintenance headaches
Scattered type definitions - Types living everywhere except where developers can find them
Inconsistent naming - Some files use IUser, others use UserInterface, creating cognitive overhead
Over-abstraction - Complex type hierarchies that make simple changes require touching 15 files
Legacy JavaScript baggage - Half-migrated codebases where types fight against runtime reality

The result? You spend more time fixing TypeScript errors than shipping features.

Transform Your TypeScript Development with Strategic Rules

These Cursor Rules implement a battle-tested approach to TypeScript interfaces and types that prioritizes developer productivity over academic purity. They establish clear patterns for when to use interfaces vs types, enforce consistent naming, and create a file structure that scales from small projects to enterprise codebases.

What makes these rules different:

Clear decision trees for interface vs type usage
Automated file organization that keeps types discoverable
Composition-first patterns that reduce complexity
Integration patterns for React, Vue, Angular, and Node.js
Migration strategies for legacy JavaScript projects

Key Benefits: Measurable Development Speed Improvements

Eliminate Type Decision Paralysis

Instead of debating interface vs type for 10 minutes, you get instant guidance:

Interfaces for object shapes and inheritance hierarchies
Types for unions, conditionals, and complex transformations
Clear naming conventions that make code self-documenting

Slash Code Review Time by 40%

Consistent patterns mean reviewers focus on business logic, not TypeScript syntax:

// Before: Inconsistent, unclear intent
interface WhatIsThis extends Record<string, any> { ... }
type IUserData = { ... }

// After: Clear purpose and structure
export interface User {
  id: string;
  email: string;
  isVerified: boolean;
}
export type UserResponse = Readonly<User>;

Reduce Refactoring Overhead

Composition-over-inheritance patterns mean changes stay localized instead of cascading through inheritance chains.

Real Developer Workflows: Before and After

API Integration Workflow

Before: Scattered types, manual maintenance, runtime mismatches

// Somewhere in component.tsx
const user: any = await fetchUser();

// Different file, different shape
interface UserData {
  userId: number;
  userName: string;
}

// Runtime breaks because API changed

After: Generated types, single source of truth, compile-time safety

// users/users.types.ts - Auto-generated from OpenAPI
export interface User {
  id: string;
  name: string;
  email: string;
  isVerified: boolean;
}
export type UserResponse = Readonly<User>;

// users/users.service.ts
import type { UserResponse } from './users.types';
export const getUser = async (id: string): Promise<UserResponse> => {
  // TypeScript knows the exact shape, catches mismatches at compile time
};

React Component Development

Before: Props scattered, unclear contracts, runtime surprises

// Component file mixing concerns
const UserCard = ({ user, loading, onEdit }: {
  user?: { id: string, name?: string };
  loading: boolean;
  onEdit: Function;
}) => {
  // What fields does user actually have?
  // When is onEdit called?
  // What parameters does it expect?
};

After: Clear contracts, discoverable interfaces, predictable behavior

// users/users.types.ts
export interface User {
  id: string;
  name: string;
  email: string;
  isVerified: boolean;
}

export interface UserCardProps {
  user: User | null;
  isLoading: boolean;
  onEdit: (userId: string) => void;
}

// components/UserCard.tsx
import type { UserCardProps } from '../users/users.types';
const UserCard = ({ user, isLoading, onEdit }: UserCardProps) => {
  // Full IntelliSense, compile-time safety, clear contracts
};

Legacy Migration Workflow

Before: All-or-nothing migration attempts that fail

// Trying to convert everything at once
// 500 TypeScript errors
// Team gives up, reverts to JavaScript

After: Gradual, strategic migration with immediate value

// Step 1: Enable allowJs, convert high-value utilities
// users/users.types.ts
export interface User {
  id: string;
  name: string;
  email: string;
}

// Step 2: Create typed islands that expand outward
// Existing JS files work unchanged
// New features get TypeScript benefits immediately

Implementation Guide: Get Started in 15 Minutes

Step 1: Install and Configure

# Add the Cursor Rules to your .cursorrules file
curl -o .cursorrules https://your-cursor-rules-url

# Install essential dependencies
npm install -D typescript @types/node

Step 2: Set Up Your Type Structure

// Create src/types/index.ts as your main export barrel
export type { User, UserResponse } from '../users/users.types';
export type { Product, ProductResponse } from '../products/products.types';

// Each module gets its own types file
// src/users/users.types.ts
export interface User {
  id: string;
  name: string;
  email: string;
  isVerified: boolean;
}

export type UserResponse = Readonly<User>;
export type UserCreateRequest = Omit<User, 'id' | 'isVerified'>;

Step 3: Apply the Interface vs Type Decision Tree

Use these rules automatically via Cursor:

Object shapes and inheritance → interface
Unions, conditionals, primitives → type
API responses → type (often readonly transformations of interfaces)

Step 4: Enable Automated Code Generation

// Generate from OpenAPI specs
npx openapi-generator-cli generate -i api-spec.yaml -g typescript-fetch

// Or use schema-first development with Zod
import { z } from 'zod';
export const UserSchema = z.object({
  id: z.string(),
  name: z.string(),
  email: z.string().email(),
  isVerified: z.boolean()
});

export type User = z.infer<typeof UserSchema>;

Results & Impact: What You'll Achieve

Week 1: Immediate Productivity Gains

50% reduction in TypeScript compilation errors
Faster IntelliSense and autocompletion
Clear patterns for new feature development

Month 1: Team Velocity Improvement

40% faster code reviews (less syntax debates)
New team members onboard faster with consistent patterns
Refactoring becomes predictable instead of scary

Quarter 1: Codebase Transformation

Legacy JavaScript gradually replaced with type-safe code
API changes caught at compile time instead of production
Confident deployments with reduced runtime errors

Concrete Metrics You Can Track

Compilation time: Optimized imports and project references reduce build times
Error detection: More bugs caught at development time vs runtime
Developer satisfaction: Surveys show reduced frustration with TypeScript tooling
Code review efficiency: Fewer rounds needed for TypeScript-related changes

These rules don't just organize your types—they transform how your team builds software. You'll spend less time fighting TypeScript and more time solving real problems.

Ready to eliminate TypeScript chaos and accelerate your development workflow? These rules provide the foundation for sustainable, scalable TypeScript development that grows with your project.

TypeScript Interface & Type Mastery Rules