JavaScript to TypeScript Converter

JavaScript Input

TypeScript Output

What Is JavaScript to TypeScript?

TypeScript adds static types to JavaScript. The JavaScript to TypeScript converter adds type annotations and converts JS to TS. Use it to migrate gradually or get a typed starting point. The TypeScript handbook defines the language.

This tool runs entirely in your browser. Nothing is sent to a server. Paste JS or upload a file; get TypeScript output. For formatting JS, use JavaScript Formatter. For validation, use JavaScript Validator. For running code, use JavaScript Console.

How to Use This Tool

Paste or Upload

Paste JavaScript into the left panel or upload a .js or .txt file. Use Sample to load example code. Use Clear to reset.

View TypeScript Output

The right panel shows TypeScript with type annotations. Types may be inferred or added as any where unclear.

Copy or Download

Use Copy or Download to get the .ts output. Review and refine types. Run tsc to validate.

JavaScript to TypeScript Examples

Here is an example of converting JavaScript to TypeScript with type annotations.

Example: Subscriber plan lookup

JavaScript input:

Input

TypeScript output:

Output

When JavaScript to TypeScript Helps

When migrating a JS project to TypeScript, this tool gives a starting point. You will need to refine types, fix any issues, and run the TypeScript compiler (tsc). Build tools like webpack, Vite, and Angular integrate TypeScript. For JSX/React, use JSX Formatter for formatting.

Frequently Asked Questions

Is my data private?

Yes. Conversion runs entirely in your browser. No data is sent to any server.

Are types accurate?

The tool infers types where possible. Complex cases may use any. Review and refine the output.

Does it support JSX?

JSX in JavaScript may be converted to TSX. Check the output. For formatting JSX, use JSX Formatter.

Can I convert TypeScript to JavaScript?

Use the TypeScript compiler (tsc) or Babel for that. This tool converts JS to TS.

What about strict mode?

The output may not satisfy strict TypeScript. Add strict flags and fix errors as needed.

Error

Success