Migration guide · js-message

Version 3.0.0 is available on npm.

Install it with npm install js-message. Review the stricter envelope validation and browser-global descriptor changes below before upgrading an existing integration.

What stays compatible

import Message from 'js-message' remains the canonical package import.
js-message/Message.js remains a supported deep ES-module path.
js-message/js-message-vanilla.js still creates globalThis.Message.
type and data remain mutable, enumerable instance fields.
JSON remains a getter and load() still returns undefined.
Buffer, boxed-string, typed-view, and custom JSON-coercible text inputs remain accepted.
The declared Node.js engine floor remains >=13.2.0.

What becomes stricter

Earlier behavior	Modernized behavior
Valid JSON such as `{}`, `[]`, or `0` could silently leave fields undefined.	Any value without an own `type` and `data` pair becomes an error envelope.
The browser global and ES-module implementations could drift.	Both surfaces share the same tested contract and recovery behavior.
Serialized native errors collapsed to `{}`.	Error JSON exposes stable `name` and `message` fields while the live value remains an `Error`.
The browser-global script installed own `JSON` and `load` properties.	They are non-enumerable prototype members, matching the ES-module class. Native `JSON.stringify()` now uses the normalized two-key envelope.

Audit code that relied on incomplete envelopes.

If your receiver intentionally sent objects without both keys, add the missing key or branch on message.type === 'error'.

An invalid cyclic or BigInt response is retained for debugging. Native serialization can still throw while that response is present; the error object itself remains serializable.

New supported conveniences

const fromObject = new Message({
    type: 'ready',
    data: { ok: true }
});

const fromJSON = new Message(
    '{"type":"ready","data":{"ok":true}}'
);

JSON.stringify(fromObject) === fromObject.JSON; // true

Constructor input, object loading, and toJSON() make js-message fit both text and structured-clone transports without replacing its original API.

Use the modern surface Read the repository migration notes