Poster

EventEmitter style wrapper around postMessage. Works with windows, iframes, and web workers.

API

post/emit and listen/addListener/on can be chained. Each channel is defined by string. There can be multiple listeners per channel.

• post(channel, ...args) - arguments after channel are passed to all listeners for that channel
• emit(channel, ...args) - alias for post
• listen(channel, callback)
• addListener(channel, callback)
• on(channel, callback)
• removeListener(channel, callback)
• removeAllListeners(channel)
• listeners(channel) - returns all listeners on the channel

Note: The API is not stable. I'm still trying to decide how close to make it to the EventEmitter API seeing as it differs in the following substatial ways:

• posting a message to an instance will not trigger the listeners on that instance
• post/emit does not return the number of listeners becuase it's hard to know how listeners are connected to the matching Poster instance in the other context and return the number of local listeners isn't useful because they won't receive the message anyways.

Howto

In order to communicate with another context (window, iframe, or web worker) two instances of Poster must be created. One in the source context and one in the destination context. The source/desintation labels are arbitrary as Poster facilitates bidirectional communication out of the box.

index.js

var iframe = document.getElementById("myIframe");
var poster = new Poster(iframe.contentWindow);

poster.post("msg", "hello, world!");

iframe.js

var poster = new Poster(wdinow.parent);

poster.on("msg", function (msg) {
    console.log("msg = " + msg);    // "msg = hello, world"
});

Future Work

• add once(channel, callback)
• automatically use iframe.contentWindow when passed an iframe
• some sort of handshaking to when the Poster instance in the other context is ready for business