What is json-to-ts and how does it work?

It's a 300-line vanilla JS tool that infers TypeScript interfaces from JSON samples, merging multiples to detect unions and optionals automatically. Paste JSON, get interfaces plus type guards — no install needed.

Does this JSON to TypeScript tool handle nested objects?

Yes, via a referenced AST where nested objects become named interfaces, preventing bloated inline types and enabling clean merging.

Is this better than quicktype for simple APIs?

For browser-based, dep-free TS-only use? Absolutely — lighter, focused, and reveals the inference guts quicktype buries.

📦 Open Source

This 300-Line Vanilla JS Beast Infers TypeScript Types from Messy JSON Like Magic

API JSON dumps got you down? One dev's 300-line vanilla JS engine turns multiple samples into sharp TypeScript interfaces, complete with runtime guards. It's the pocket rocket quicktype wishes it was.

theAIcatchup Apr 11, 2026 4 min read

Live demo screenshot of json-to-ts generating TypeScript interfaces from JSON samples

⚡ Key Takeaways

A tiny AST and recursive mergeTypes function unlock smart inference from multiple JSON samples 𝕏
Optionals emerge naturally—no hacks—making merged interfaces feel intuitive 𝕏
Bonus type guards from the same AST turn static types into runtime safety nets 𝕏

Published by

theAIcatchup

Ship faster. Build smarter.

#JSON to TypeScript #TypeScript inference #type inference #type-guards #typescript #vanilla JavaScript

Worth sharing?

Get the best Developer Tools stories of the week in your inbox — no noise, no spam.

Originally reported by dev.to

⚡ Key Takeaways

The 60-Second TL;DR

theAIcatchup

Share this article

Worth sharing?

Related Stories

Zephyr Events: 2KB Emitter That Won't Ghost Your Handlers

Valicore: Zero-Dep Runtime Validation That Actually Sticks for TypeScript Teams

TypeScript Patterns That Stopped Me From Quitting Frontend Dev

Docker: Fixing TypeScript AI Agent Nightmares

Stay in the loop