JSON to TypeScript
Generate TypeScript interfaces from JSON objects with automatic type inference
Enter or paste JSON object to convert
Generated TypeScript interface definition
What is JSON to TypeScript Conversion?
JSON to TypeScript conversion automatically generates TypeScript interface definitions from JSON data. This tool analyzes your JSON structure, infers types for each property, and creates type-safe TypeScript interfaces that you can use in your projects. It's essential for working with APIs, ensuring type safety, and improving developer experience with autocomplete and error checking.
How to Use the JSON to TypeScript Generator
- Paste your JSON object into the input field
- Optionally customize the interface name (default: "GeneratedInterface")
- Toggle optional fields and sorting options as needed
- Click "Generate Interface" to create the TypeScript definition
- Copy the generated interface to use in your TypeScript project
Example: Before and After Conversion
Input (JSON):
{
"user": {
"id": 123,
"name": "John Doe",
"email": "john@example.com",
"isActive": true,
"roles": ["admin", "user"],
"metadata": null
},
"timestamp": "2024-01-15T10:30:00Z"
}Output (TypeScript Interface):
interface User {
id?: number;
name?: string;
email?: string;
isActive?: boolean;
roles?: string[];
metadata?: null;
}
interface GeneratedInterface {
user?: User;
timestamp?: string;
}The generated interfaces provide full type safety and can be used immediately in your TypeScript code for API responses, data models, or configuration objects.
Key Features
- Automatic Type Inference: Detects strings, numbers, booleans, arrays, and nested objects
- Nested Object Support: Generates separate interfaces for nested structures
- Array Type Detection: Handles arrays of primitives, objects, and mixed types
- Special Character Handling: Properly escapes property names with special characters
- Customizable Options: Control interface names, optional fields, and field sorting
- 100% Client-Side: Your data never leaves your browser
When to Use JSON to TypeScript
- API Integration: Generate types for API responses to ensure type safety
- Data Modeling: Create TypeScript models from example JSON data
- Migration Projects: Convert JavaScript projects to TypeScript faster
- Documentation: Generate type definitions for configuration files
- Code Generation: Bootstrap TypeScript interfaces from sample data
TypeScript Interface Best Practices
- Review generated interfaces and adjust optional fields based on your API contract
- Consider using union types for fields with specific allowed values
- Add JSDoc comments to generated interfaces for better documentation
- Use meaningful interface names that describe the data structure
- Combine multiple related interfaces into a single file for better organization
- Consider using 'readonly' for properties that shouldn't be modified
Understanding Generated Types
Primitive Types:
string- For text valuesnumber- For integers and floating-point numbersboolean- For true/false valuesnull- For explicit null values
Complex Types:
string[]- Array of stringsCustomInterface[]- Array of objects(string | number)[]- Array with mixed typesany[]- Empty array (type unknown)
Optional Fields:
Fields marked with ? are optional, meaning they may or may not be present
in the object. This is useful for API responses where some fields might be omitted.
You can disable this feature if you want all fields to be required.
Frequently Asked Questions
What is a TypeScript interface?
A TypeScript interface is a way to define the structure of an object in TypeScript. It specifies what properties an object should have and what types those properties should be. Interfaces help catch type errors during development and provide better code documentation and autocomplete in your IDE.
How does the JSON to TypeScript converter work?
The converter analyzes your JSON data structure and automatically infers the types of each property. It detects strings, numbers, booleans, null values, arrays, and nested objects. For nested objects, it generates separate interfaces. The tool handles special characters in property names and creates valid TypeScript syntax.
Why are all fields marked as optional?
By default, all fields are marked with '?' to make them optional. This is a safe default because JSON data from APIs might not always include every field. You can disable this behavior using the 'Use Optional Fields' toggle if you want all fields to be required in your TypeScript code.
Can I customize the interface name?
Yes! The default interface name is 'GeneratedInterface', but you can change it to any valid TypeScript identifier using the interface name input field. This is useful when you want to give your interface a meaningful name like 'User', 'Product', or 'ApiResponse'.
How does it handle nested objects?
When your JSON contains nested objects, the tool automatically generates separate interfaces for each nested level. For example, if you have a 'user' object with an 'address' object inside it, you'll get both a 'User' interface and an 'Address' interface. The nested interfaces are placed before the main interface in the output.
What happens with arrays in my JSON?
The tool analyzes array contents to determine the element type. For arrays of primitives (strings, numbers, booleans), it generates simple array types like 'string[]' or 'number[]'. For arrays of objects, it creates an interface for the object structure and uses it as the array type. Mixed-type arrays become union types like '(string | number)[]'.
Is my JSON data sent to a server?
No, all processing happens entirely in your browser. Your JSON data never leaves your device, ensuring complete privacy and security for sensitive information. This also means the tool works offline once the page is loaded.
Can I use the generated interfaces in my project?
Absolutely! The generated TypeScript interfaces are production-ready and can be copied directly into your TypeScript files. They follow TypeScript best practices and will work with any TypeScript project. You may want to review and adjust optional fields or interface names based on your specific needs.
What if my JSON has special characters in property names?
The tool handles special characters automatically. Property names with spaces, hyphens, or other special characters are wrapped in quotes in the generated interface. For example, 'user-name' becomes '"user-name"?: string;'. This ensures the generated TypeScript is always syntactically valid.
How do I handle union types or more complex scenarios?
The tool provides a good starting point, but you may need to refine the generated interfaces for complex scenarios. For example, if a field can be multiple specific string values, you might want to change 'string' to a union type like '"active" | "inactive"'. The generated code is meant to be a foundation that you can customize for your specific use case.