RemoteDocumentMessaging

Overview

This document describes a proposal for discovering and communicating with "remote" documents. In particular, this proposal lets a web page communicate with another document even if the web page does not have a direct script connection to that document.

Use Cases

The user opens the same word processing document hosted by a document editing web site in two different browser windows. The document editing web site wants to ensure that edits in one window a reflected in the other window without needing to round-trip through the server (e.g., because the user is offline). Unfortunately, the documents are in different units of related browsing contexts, which means the two documents cannot form a direct script connection. Using remote document messaging, the two documents can discover each other and update each other about edits performed by the user.

Specification

[Constructor(DOMString name)]
interface BroadcastChannel : EventTarget {
    void postMessage(any message);
    void close();

    attribute EventHandler onmessage;
};

Examples

// The channel name, "deep-thoughts", is scoped to the current origin.
var channel = new BroadcastChannel("deep-thoughts");

channel.addEventListener("message", function(message) {
  // Do something interesting with |message|, which is a MessageEvent.
}, false);

// Send a message to each other BroadcastChannel instance with the same channel
// name in the same origin.
channel.postMessage("I think, therefore I am.");

Notes

You can already accomplish this through localStorage as that broadcasts storage events: http://bens.me.uk/2013/localstorage-inter-window-messaging Something that does not involve synchronous IO would probably be better though.