Majik CJSON

Lightweight gzip-compressed JSON container with magic-byte framing.
Compress, export, and restore typed JSON payloads as Blob, ArrayBuffer, or base64 — built for Cloudflare Workers and browser environments.

const cj = MajikCompressedJSON.create({ id: 1, messages: [...] });
const blob = cj.toMJKCJSON();                                    // upload to R2
const back = await MajikCompressedJSON.decompress<MyType>(blob); // restore original

Table of Contents

• Majik CJSON
  • Table of Contents
  • Overview
  • Features
  • Installation
  • Usage
    • Import
    • Create a compressed container
    • Export the compressed payload
    • Restore from a compressed payload
    • High-level decompress wrapper
    • Probe without decompressing
    • Introspection getters
  • API Reference
    • MajikCompressedJSON<T>
      • Static methods
      • Instance methods
      • Getters
      • Types
  • Binary Format
  • Contributing
  • License
  • Author
  • About the Developer
  • Contact

Overview

majik-cjson wraps any JSON object or array into an immutable, gzip-compressed binary container. Every payload is framed with a 4-byte magic header (MJKC) that allows fast identity probing without full decompression.

The container can be exported as a Blob (for object storage uploads), an ArrayBuffer (for raw binary handling), or a base64 string (for embedding in JSON fields or URLs). Any of those forms can be fed back into fromMJKCJSON() to restore the original typed payload.

It is a single-dependency package (fflate) with no WASM, no native bindings, and no Node.js-only APIs — it runs anywhere that has TextEncoder, Blob, and atob/btoa.

Features

• gzip compression via fflate — pure JS, no WASM, no cold-start overhead
• Magic-byte framing — every payload starts with MJKC (0x4D 0x4A 0x4B 0x43) for cheap identity probing
• Typed generics — full T support so your payload type flows through compress → decompress
• Flexible I/O — accepts and exports Blob, ArrayBuffer, Uint8Array, and base64 strings
• Immutable instances — private constructor + JS # private fields; state is truly inaccessible at runtime
• Input validation — throws descriptive errors on invalid JSON, bad magic headers, and decompression failures
• Zero Node.js dependency — works in Cloudflare Workers, browsers, and any Web API–compatible runtime
• Compression introspection — compressionRatio and byteSize getters for observability

Installation

npm install majik-cjson

pnpm add majik-cjson

yarn add majik-cjson

Requirements: ESM-compatible runtime with TextEncoder, Blob, atob/btoa (Cloudflare Workers, modern browsers, Node.js ≥ 18).

Usage

Import

import { MajikCompressedJSON } from "majik-cjson";

Create a compressed container

Pass a plain object, array, or a valid JSON string. An error is thrown for invalid input.

// From an object
const cj = MajikCompressedJSON.create({ id: 1, name: "Zelijah" });

// From an array
const cj = MajikCompressedJSON.create([1, 2, 3]);

// From a JSON string
const cj = MajikCompressedJSON.create('{"id":1,"name":"Zelijah"}');

// With a custom type
type ThreadExport = { threadId: string; messages: Message[] };
const cj = MajikCompressedJSON.create<ThreadExport>(exportPayload);

Export the compressed payload

// Blob — for uploading to Cloudflare R2 or any object store
const blob = cj.toMJKCJSON();
await r2.put("exports/thread-123.mjkcjson", blob);

// ArrayBuffer — for raw binary handling or passing directly to fetch()
const buffer = cj.toBinary();

// Base64 string — for embedding in JSON fields, database columns, or URLs
const b64 = cj.toBase64();

// Plain object with both payloads (base64-encoded compressed form)
const obj = cj.toJSON();
// → { payload: { ... }, compressed: "MJKC..." }

Restore from a compressed payload

fromMJKCJSON() accepts any form — Blob, ArrayBuffer, Uint8Array, or base64 string.

// From Blob (e.g. fetched from R2)
const instance = await MajikCompressedJSON.fromMJKCJSON<ThreadExport>(blob);

// From base64 string
const instance = await MajikCompressedJSON.fromMJKCJSON<ThreadExport>(b64);

// From ArrayBuffer
const instance = await MajikCompressedJSON.fromMJKCJSON<ThreadExport>(buffer);

// Access the original payload
console.log(instance.payload); // ThreadExport

High-level decompress wrapper

If you only need the original payload and don't need the instance, use decompress() directly.

const original = await MajikCompressedJSON.decompress<ThreadExport>(blob);
console.log(original.threadId);

Probe without decompressing

isCompressed() checks the magic header cheaply — no decompression, no JSON parsing.

const valid = await MajikCompressedJSON.isCompressed(blob); // true | false

Useful as a pre-flight guard before calling fromMJKCJSON(), e.g. when processing user-uploaded files.

Introspection getters

const cj = MajikCompressedJSON.create(largePayload);

cj.payload           // T — original deserialized JSON
cj.compressedBytes   // Uint8Array — framed binary (MAGIC + gzip)
cj.byteSize          // number — byte size of compressed payload
cj.compressionRatio  // number — compressedSize / originalSize (lower = better)
cj.isEmpty           // boolean — true if compressed payload is empty

console.log(`Reduced by ${((1 - cj.compressionRatio) * 100).toFixed(1)}%`);
// → "Reduced by 87.3%"

API Reference

MajikCompressedJSON<T>

Static methods

| Method | Description | | --------------------------------------- | ----------------------------------------------------------------------------------------------- | | create<T>(input: JSONInput) | Compress a JSON object, array, or JSON string. Returns a new MajikCompressedJSON<T> instance. | | fromMJKCJSON<T>(input: MJKCJSONInput) | Reconstruct an instance from a Blob, ArrayBuffer, Uint8Array, or base64 string. | | decompress<T>(input: MJKCJSONInput) | Convenience wrapper — decompresses and returns the payload directly. | | isCompressed(input: MJKCJSONInput) | Returns true if the input has a valid MJKC magic header. No decompression performed. |

Instance methods

| Method | Returns | Description | | -------------- | ------------------------------------ | ------------------------------------------------------------------------------------------ | | toMJKCJSON() | Blob | Framed binary as a Blob (application/octet-stream). Use for R2 / object store uploads. | | toBinary() | ArrayBuffer | Framed binary as an ArrayBuffer. | | toBase64() | string | Framed binary encoded as base64. | | toJSON() | { payload: T; compressed: string } | Plain serialisable object with both payloads. |

Getters

| Getter | Type | Description | | ------------------ | ------------ | -------------------------------------------------------------------------- | | payload | T | The original deserialized JSON payload. | | compressedBytes | Uint8Array | The framed compressed binary. | | byteSize | number | Byte size of the compressed payload. | | compressionRatio | number | compressedSize / originalSize. Lower is better. | | isEmpty | boolean | true if the compressed payload contains no data beyond the magic header. |

Types

type JSONInput    = Record<string, unknown> | unknown[] | string;
type MJKCJSONInput = Blob | ArrayBuffer | Uint8Array | string;

Binary Format

Every MJKCJSON payload follows this layout:

┌─────────────────────┬──────────────────────────────────────┐
│  MAGIC (4 bytes)    │  gzip-compressed JSON (variable)     │
│  4D 4A 4B 43        │  fflate gzipSync, level 6            │
│  "M" "J" "K" "C"   │                                      │
└─────────────────────┴──────────────────────────────────────┘

The magic header allows format detection without decompression. The gzip payload is standard RFC 1952 — compatible with any gzip implementation.

Contributing

If you want to contribute or help extend support to more platforms, reach out via email. All contributions are welcome!

License

Apache-2.0 — free for personal and commercial use.

Author

Made with 💙 by @thezelijah

About the Developer

• Developer: Josef Elijah Fabian
• GitHub: https://github.com/jedlsf
• Project Repository: https://github.com/Majikah/majik-cjson

Contact

• Business Email: [email protected]
• Official Website: https://www.thezelijah.world