JSON to TypeScript Interface Converter

Convert raw JSON objects into strongly-typed TypeScript interfaces or type aliases. Supports recursive nested structures, arrays, and optional field modifiers.

Input JSON

Sample Schemas
TypeScript Output
2 Interfaces

Interfaces

2

Properties

10

Syntax

Interface

Target

TS 5.x

Generated TypeScript Definitions257 chars
export interface UserProfile {
  id: string;
  username: string;
  email: string;
  isActive: boolean;
  profile: Profile;
  roles: string[];
}

export interface Profile {
  firstName: string;
  lastName: string;
  avatarUrl: string;
  reputation: number;
}

Compile-Time Type Safety Guarantee

Ensures zero runtime key mismatch errors. Ready for drop-in use in Next.js, React, Node.js, and Express API routes.

Algebraic Type Theory & TypeScript AST Inference Formulations

Mapping untyped JSON data to TypeScript static types evaluates structural product types through recursive type inference:

1. Recursive JSON Value Type Inference Function
τ(V) = (V ∈ String ⇒ string) ∨ (V ∈ Number ⇒ number) ∨ (V ∈ Array ⇒ τ(E)[]) ∨ Interface_K
2. Product Type Interface Composition Equation
Type(O) = ⨂_{i=1}^n ( k_i : τ(v_i) )
Step-by-Step Type Inference & AST Generation Breakdown
Step 1: AST Lexical Evaluation & Type Mapping
Inspect primitive values to determine string, number, boolean, null.
Step 2: Recursive Extraction of Child Objects
Extract nested objects into separate interfaces with PascalCase naming convention.
Step 3: Interface Construction & Export
Result=Strict, Zero-Error TypeScript Definition

JSON Primitives to TypeScript Types Reference

JSON ValueTypeScript TypeExample OutputStatic Compile Behavior
"Hello"stringtitle: string;UTF-16 string primitive
42, 3.14numberprice: number;IEEE 754 64-bit float
true / falsebooleanisActive: boolean;Binary boolean state
{ ... }Interface / Typeprofile: Profile;Structured object type
[ ... ]T[]roles: string[];Homogeneous array collection

Frequently Asked Questions

How does the converter handle nested objects?
The converter recursively traverses nested objects and automatically extracts discrete named interfaces for each nesting level. For example, a user object containing an address sub-object produces both `User` and `Address` interfaces with typed references.
What about arrays of objects?
Arrays are inspected and typed as `T[]`. If the array contains objects, an interface is generated for the element schema and referenced as an array type.
Can I customize the generated interface names?
Yes. You can specify the root interface name directly in the control panel. Nested interface names are automatically derived by capitalizing their corresponding JSON object keys.
Is my JSON data transmitted to any external server?
No. All parsing, recursive AST traversal, and TypeScript code generation take place 100% locally in your browser memory.

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