JavaScript to TypeScript Converter
Convert JavaScript to TypeScript with type annotations
JavaScript Input
TypeScript Output
What is JavaScript to TypeScript Converter?
Need to migrate your JavaScript code to TypeScript? This tool converts your JavaScript code to TypeScript by adding type annotations, interfaces, and proper TypeScript syntax. Perfect for modernizing your codebase or taking advantage of TypeScript's type safety features.
According to TypeScript documentation, TypeScript adds static type checking to JavaScript, making code more maintainable and catching errors at compile time. Our converter analyzes your JavaScript code and adds appropriate type annotations, making the migration process much easier.
Everything happens in your browser – your code never leaves your computer. Convert, download, and use your TypeScript code right away.
What Makes This Tool Different
Automatic Type Inference
We analyze your JavaScript code and automatically add type annotations. Variables, function parameters, and return types are inferred from your code structure.
Interface Generation
Object structures are converted to TypeScript interfaces. Makes your code more type-safe and easier to understand.
Type Safety
Converted TypeScript code includes proper types, making it easier to catch errors before runtime. TypeScript's compiler will help you find issues early.
File Upload Support
Got a big file? Just upload it. Works great for converting those massive JavaScript files or entire modules without copy-pasting.
Download TypeScript
One click to download your TypeScript file. Drop it into your TypeScript project and start benefiting from type safety.
Syntax Validation
We validate your JavaScript before converting. Invalid code gets caught early, so you know the TypeScript version will work correctly.
How It Works
Paste or Upload JavaScript
Paste your JavaScript code into the left editor, or click "Upload" to load a file. You can also click "Sample" to see an example. The tool accepts any valid JavaScript code.
Automatic Conversion
As soon as you paste, the converter processes your JavaScript and displays the TypeScript version on the right. Type annotations are added, interfaces are generated, and the code is properly formatted.
Download or Copy
Click "Download" to save the TypeScript file, or "Copy" to copy it to your clipboard. The TypeScript code is ready to use in your project.
When You'd Actually Use This
Code Migration
Migrate existing JavaScript projects to TypeScript. Gradually convert your codebase to take advantage of TypeScript's type safety and better tooling.
Type Safety
Add type safety to your JavaScript code. TypeScript catches errors at compile time, making your code more reliable and easier to maintain.
Better IDE Support
TypeScript provides better autocomplete, refactoring, and navigation in IDEs. Convert your JavaScript to get these benefits.
Team Collaboration
TypeScript makes code more self-documenting. Types serve as documentation, making it easier for team members to understand your code.
Common Questions
Is my JavaScript code stored?
Nope. Everything happens right in your browser. Your code never leaves your computer – we don't even see it.
Does the conversion preserve functionality?
Yes. The converted TypeScript code works exactly the same as your original JavaScript. We only add type annotations – no logic changes.
Are all types inferred correctly?
We do our best to infer types from your code, but you may need to manually adjust some types for complex cases. Review the output and refine as needed.
Does it work with ES6+ features?
Yes, we support modern JavaScript syntax including ES6+, async/await, arrow functions, classes, and more. If it's valid JavaScript, we can convert it.
Can I convert TypeScript back to JavaScript?
TypeScript compiles to JavaScript, so you can use the TypeScript compiler (tsc) to generate JavaScript. But for direct conversion, you'd need to manually remove types.
Does it work with large files?
Yep. Since everything happens in your browser, it depends on your device. Small files convert instantly. Very large files (several MB) might take a few seconds.
Other JavaScript Tools You Might Need
Conversion is just one JavaScript task. Here are other tools that work well together:
Need to learn more about TypeScript? Check out the official TypeScript documentation or the comprehensive guide on MDN.