Convert JavaScript to TypeScript with houtini-lm

Quick Start

Jump straight into TypeScript conversion with these ready-to-use prompts:

Please convert this JavaScript file to TypeScript: C:/project/src/UserService.js

Convert this legacy JavaScript to strict TypeScript with type guards: C:/legacy/oldCode.js

Convert this React component to TypeScript with proper props typing: C:/components/Dashboard.jsx

Analyze this project for TypeScript conversion readiness: C:/my-project/src

What It Does

Imagine having a TypeScript expert who's memorised every best practice, pattern, and modern feature convert your JavaScript code whilst you focus on building features. convert_to_typescript intelligently transforms your JavaScript into production-ready TypeScript with comprehensive type annotations and modern best practices.

This isn't just a find-and-replace operation. It's sophisticated code transformation that:

• Infers Types Intelligently - Analyses your code patterns to generate meaningful type definitions
• Adds Modern Patterns - Uses the latest TypeScript features like template literals, conditional types, and mapped types
• Preserves Functionality - Your code works exactly the same, just with type safety
• Follows Best Practices - Generates code that passes strict TypeScript checks and code reviews
• Creates Supporting Infrastructure - Includes tsconfig.json, type definitions, and migration guides

The conversion process understands your project context, framework patterns, and coding style to produce TypeScript that feels like it was written by your team from day one.

Parameters

Customise your TypeScript conversion to match your project's needs and coding standards:

*Either filePath or code is required - use filePath for files, code for snippets

Real-World Examples

Here's how to handle common conversion scenarios:

Legacy Codebase Modernisation

houtini-lm:convert_to_typescript with:
- filePath: "C:/legacy-project/src/utils/DataProcessor.js"
- projectPath: "C:/legacy-project"
- strict: true
- target: "ES2022"
- addTypeGuards: true
- useInterfaces: true

React Component Migration

houtini-lm:convert_to_typescript with:
- filePath: "C:/react-app/src/components/UserProfile.jsx"
- target: "ES2020"
- strict: true
- useInterfaces: true
- addTypeGuards: false

Node.js API Conversion

houtini-lm:convert_to_typescript with:
- filePath: "C:/api/routes/userController.js"
- projectPath: "C:/api"
- target: "ES2022"
- strict: true
- addTypeGuards: true

Quick Function Conversion

houtini-lm:convert_to_typescript with:
- code: "function calculatePrice(item, discount) { return item.price * (1 - discount); }"
- strict: true
- addTypeGuards: true

Gradual Migration Approach

houtini-lm:convert_to_typescript with:
- filePath: "C:/mixed-project/src/helpers/utils.js"
- strict: false
- target: "ES2020"
- addTypeGuards: false
- useInterfaces: false

What You Get Back

The conversion delivers everything you need for professional TypeScript development:

🎯 Complete TypeScript Files

• Fully typed .ts/.tsx files with proper syntax and conventions
• Comprehensive type annotations for parameters, return values, and variables
• Modern TypeScript features using the latest language capabilities
• Clean, readable code that follows TypeScript best practices

🏗️ Type Infrastructure

• Interface definitions for complex objects and API responses
• Type aliases for reusable type patterns
• Generic type definitions for flexible, type-safe code
• Enum definitions for strongly-typed constant values

🔒 Runtime Type Safety

• Type guard functions for safe runtime type checking
• Assertion functions for validating assumptions
• Union and intersection types for complex type compositions
• Utility types customised for your codebase patterns

📚 Enhanced Documentation

• TSDoc comments with comprehensive parameter and return type information
• Usage examples showing how to use the typed functions
• Migration notes explaining any changes made during conversion
• Best practices guidance embedded in comments

⚙️ Configuration and Setup

• tsconfig.json optimised for your project needs
• Package.json updates with TypeScript dependencies
• Build script modifications for TypeScript compilation
• IDE configuration hints for the best development experience

TypeScript Features Generated

The conversion leverages the full power of modern TypeScript:

🧩 Advanced Type System Features

• Conditional Types - Complex type logic based on conditions
• Mapped Types - Transform existing types into new variations
• Template Literal Types - Type-safe string manipulation
• Discriminated Unions - Safe handling of variant types

🚀 Modern Language Patterns

• Optional Chaining & Nullish Coalescing - Safe property access
• Private Class Fields - True encapsulation in classes
• Decorators - When enabled in target configuration
• Async/Await with proper Promise typing

🎨 Framework-Specific Integrations

The conversion recognises and optimises for popular frameworks:

React Integration

• Component Props Interfaces - Proper typing for component properties
• Hook Typing - useState, useEffect, and custom hooks with generics
• Event Handler Types - Properly typed onClick, onChange handlers
• Ref Typing - Type-safe useRef and forwardRef usage

Node.js Integration

• Built-in Module Types - Proper typing for fs, path, http modules
• Express.js Types - Request, Response, and middleware typing
• Environment Variables - Type-safe process.env usage
• Async Patterns - Promise-based APIs with proper error handling

Vue.js Integration

• Component Options Typing - Props, computed, methods with types
• Composition API - Reactive properties with proper inference
• Template Refs - Type-safe template reference handling
• Vuex/Pinia - State management with comprehensive typing

Perfect Use Cases

Here's when TypeScript conversion becomes your productivity superpower:

📈 Legacy Code Modernisation

Transform years-old JavaScript codebases into modern, maintainable TypeScript. Perfect for when you're finally ready to tackle that technical debt and add the type safety you've always wanted.

🎯 Team Productivity Enhancement

Enable better IDE support, catch errors at compile time instead of runtime, and make your codebase more self-documenting. New team members will thank you for the improved developer experience.

🔒 Error Prevention Strategy

Stop debugging undefined property errors and type mismatches. TypeScript catches these issues during development, saving hours of runtime debugging and production hotfixes.

🚀 Scaling Preparation

Before your codebase grows too large to manage, add type safety that makes refactoring confident rather than terrifying. Essential for growing teams and evolving products.

🔄 Framework Migration Support

When moving from one framework to another, TypeScript provides a stable foundation with clear interfaces and contracts that make migrations more predictable.

📖 Documentation Through Code

Types serve as living documentation that never goes out of date. Future maintainers (including yourself) will understand the code's intention without extensive comments.

🤝 API Integration Improvement

Convert your API clients to TypeScript and get compile-time validation of request/response structures. No more guessing what fields are available or required.

Best Practices

Get the most from your TypeScript conversion with these proven strategies:

🎯 Start Strategic, Think Incremental

Don't try to convert everything at once. Start with these high-impact areas:

• Utility functions first - Pure functions convert cleanly and provide immediate value
• API interfaces next - Define your data contracts early for maximum benefit
• Core business logic - Where type safety prevents the most expensive bugs
• Framework components last - Once you're comfortable with TypeScript patterns

⚙️ Configuration Strategy

Match your TypeScript settings to your team's experience and project needs:

• New projects - Use strict: true for maximum safety
• Legacy migration - Start with strict: false, gradually tighten
• Team onboarding - Begin with addTypeGuards: false to reduce complexity
• Production systems - Always use useInterfaces: true for clear contracts

🔧 Framework-Specific Tips

React Projects

• Always include component context in your prompts
• Convert PropTypes to interface definitions first
• Use function components over class components for better type inference
• Specify hook types explicitly: useState<User | null>(null)

Node.js APIs

• Define request/response interfaces before converting route handlers
• Use strict mode for database models and business logic
• Type your middleware functions for better composition
• Include error type definitions for proper error handling

🧪 Testing Integration

• Convert tests alongside - Use the same function to convert your Jest/Mocha tests
• Type your mocks - Ensure test doubles match production interfaces
• Use type assertions carefully - Prefer type guards over as casting
• Test type safety - Write tests that verify your types work as expected

👥 Team Adoption Strategy

• Train incrementally - Start with basic typing, advance to complex patterns
• Document your decisions - Keep notes on type choices and conventions
• Set up tooling - Configure VSCode/WebStorm for the best TypeScript experience
• Review together - Use type definitions as learning opportunities

Troubleshooting

Common issues and their solutions: