justmessage-rpc

This fork:

• removes JSON.stringify/parse from the core library.
• removes IMessageEvent and all other DOM assumptions.
• renames readMessages to recvMessage for parity with postMessage.
• adds defaultPostable so that the library can be used as-is in iframes.
• removes origin from the core library due to the existence of serviceIds.

Install with npm install --legacy-peer-deps

This is a library for making RPC calls (asynchronous method calls) between browser windows or iframes. It builds upon the browser postMessage API, which lacks some features that complex applications may depend upon:

• The ability to have transactional request/response calls between windows
• Easy scoping between multiple applications; postMessage events are global on the window, so multiple postMessage targets must be disambiguated.
• postMessage does not guarantee ordering, which can lead to surprising and difficult to diagnose bugs.

This RPC layer resolves those issues.

Example Usage

The RPC class is symmetrical and should be created on both windows you want to talk between. Say you want to embed iframe.html inside the parent.html, and have the parent provide a function that adds things the child gives it. That might look like:

parent.js

import { RPC } from 'justmessage-rpc';

const rpc = new RPC({
  // The window you want to talk to:
  target: myIframe.contentWindow,
  // This should be unique for each of your producer<->consumer pairs:
  serviceId: 'my-awesome-service',

  // Optionally, allowlist the origin you want to talk to:
  // origin: 'example.com',
});

rpc.expose('add', (data) => data.a + data.b);

iframe.js

import { RPC } from 'justmessage-rpc';

const rpc = new RPC({
  target: window.parent,
  serviceId: 'my-awesome-service',
});

rpc.call('add', { a: 3, b: 5 }).then(result => console.log('3 + 5 is', result));