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How to Convert JavaScript to TypeScript - Step by Step Guide

Step 1

Input Your JavaScript Code

Let's convert your JavaScript to TypeScript! You have several options:

•
Paste directly: Copy your JavaScript code and paste it into the input editor
•
Upload a file: Click "Upload" to select a .js file from your computer
•
Try the sample: Click "Sample" to see conversion in action

Example: JavaScript Input

Here's JavaScript code before conversion:

function greet(name) {
  return "Hello, " + name;
}
Step 2

Automatic Type Inference

The converter analyzes your code and adds TypeScript types:

•
Infers parameter types: Analyzes function parameters and adds appropriate types
•
Adds return types: Detects function return values and annotates them
•
Generates interfaces: Creates TypeScript interfaces for objects

Example: TypeScript Output

The same code with TypeScript types:

function greet(name: string): string {
  return "Hello, " + name;
}
Step 3

Review Generated Types

Check and refine the automatically generated TypeScript code:

•
Verify types: Ensure inferred types match your intentions
•
Syntax highlighting: Color-coded TypeScript for easy review
•
Edit if needed: Manually adjust types for complex scenarios
Step 4

Export TypeScript Code

Save your converted TypeScript code:

•
Copy to clipboard: One-click copying for your TypeScript project
•
Download as file: Save as a .ts file for immediate use
•
TypeScript ready: Code is ready for your TypeScript compiler

Frequently Asked Questions

Can this tool convert JavaScript to TypeScript automatically?

Yes, the tool analyzes your JavaScript code and automatically adds TypeScript type annotations based on usage patterns. However, complex types may require manual review and adjustment for optimal type safety.

Will the converted TypeScript code work immediately?

The converted code will work with TypeScript compiler in most cases. However, you may need to refine some types, add missing imports, or adjust generic types for complex scenarios. Always test the converted code in your project.

What types does the converter infer?

The converter infers basic types like string, number, boolean, arrays, and objects. It analyzes function parameters and return values to suggest appropriate types. Complex types like unions, generics, and advanced TypeScript features may need manual addition.

Should I convert all JavaScript files to TypeScript?

Converting to TypeScript provides better type safety, improved IDE support, and catches errors at compile time. It's beneficial for large projects and team collaboration. Start with core modules and gradually convert other files.

Can I convert TypeScript back to JavaScript?

Yes, TypeScript compiles to JavaScript. You can use the TypeScript compiler (tsc) to transpile TypeScript back to JavaScript, though you'll lose the type annotations. This is commonly done for browser deployment.

Is the JavaScript to TypeScript converter completely free?

Yes, totally free with no limitations on file size or usage frequency. No registration required, and you can convert unlimited JavaScript files to TypeScript with automatic type inference.