superjson

JSON superset that serializes JavaScript's full type system — safely transport Dates, Maps, Sets, BigInts, and undefined over the wire.

superjson

General JS

JSON superset that serializes JavaScript's full type system — safely transport Dates, Maps, Sets, BigInts, and undefined over the wire.

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Fit

Bundle (gzip)

3.9 kB

10.8 kB raw

Install size includes transitive dependencies. Bundle size is gzipped browser payload.

Freshness

The Problem

JSON.stringify loses Date objects (converts to strings), drops undefined values, and can't handle Map, Set, RegExp, or BigInt. Deserializing API responses requires manual date reconstruction throughout your codebase.

What It Does

SuperJSON serializes any JavaScript value to a JSON-compatible format that includes type metadata. superjson.parse() reconstructs the original types exactly — a Date comes back as a Date, a Map as a Map. Used by tRPC and Blitz.js as the default serialization layer.

Installation

bash
npm install superjson

Usage Example

typescript
import superjson from 'superjson';

const data = {
  createdAt: new Date('2025-01-15'),
  tags: new Set(['react', 'typescript']),
  meta: new Map([['version', 2]]),
  count: BigInt(9007199254740993),
};

const json = superjson.stringify(data);
// '{"json":{"createdAt":"2025-01-15T00:00:00.000Z",...},"meta":{"values":{"createdAt":["Date"],...}}}'

const restored = superjson.parse<typeof data>(json);
restored.createdAt instanceof Date; // true
restored.tags instanceof Set;       // true

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