⚡ JavaScript to TypeScript Converter Online

Convert JS to TypeScript instantly with automatic type inference

🚀 How It Works

Paste your JavaScript code on the left, click "Convert to TypeScript", and get TypeScript code with type annotations on the right. The converter adds types, interfaces, and proper TypeScript syntax automatically.

📝 JavaScript Input
✨ TypeScript Output

⚠️ Note

This is a basic converter that adds type annotations. For complex projects, manual review and adjustment of types is recommended. Use TypeScript compiler for production code.

Features of Our JS to TS Converter

🎯 Type Inference

Automatically infers types from JavaScript code and adds appropriate TypeScript annotations.

📦 Interface Generation

Creates TypeScript interfaces for objects and complex data structures.

⚡ Instant Conversion

Convert JavaScript to TypeScript in real-time without server uploads.

🔒 100% Private

All processing happens in your browser. Your code never leaves your device.

Why Convert JavaScript to TypeScript?

Conversion Examples

Example 1: Function with Parameters

JavaScript:

function add(a, b) {
  return a + b;
}

TypeScript:

function add(a: number, b: number): number {
  return a + b;
}

Common Conversion Patterns

Here are common JavaScript patterns and their TypeScript equivalents:

Variables & Constants

JS: const name = 'John';

TS: const name: string = 'John';

Arrays

JS: const numbers = [1, 2, 3];

TS: const numbers: number[] = [1, 2, 3];

Objects

JS: const user = { name: 'John', age: 30 };

TS: const user: { name: string; age: number } = { name: 'John', age: 30 };

Classes

JS: class Person { constructor(name) { this.name = name; } }

TS: class Person { name: string; constructor(name: string) { this.name = name; } }

Best Practices for Migration

  1. Start with tsconfig.json: Configure TypeScript compiler options
  2. Rename files gradually: Change .js to .ts one file at a time
  3. Use 'any' initially: Add proper types incrementally
  4. Enable strict mode: Gradually enable stricter type checking
  5. Add type definitions: Install @types packages for libraries
  6. Test thoroughly: Ensure functionality remains unchanged

Frequently Asked Questions

Q: Is the conversion 100% accurate?

A: Basic conversions are accurate, but complex code may need manual type adjustments. Always review and test converted code.

Q: Can I convert entire projects?

A: This tool is best for individual files. For full projects, use TypeScript's migration tools or convert files incrementally.

Q: Will my JavaScript code still work?

A: Yes, TypeScript is a superset of JavaScript. Valid JavaScript is valid TypeScript (though it may need type annotations).

Q: Do I need to install anything?

A: No, this online converter works entirely in your browser. For development, install TypeScript via npm.

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