Installation

npm install window-bus --save

Description

An ultra light (2Kb) library to facilitate communication between iframes, regardless of origin

Example

You can have a look at the test folder on github which contains a runnable basic example

To run the demo, clone the git repository then run npm install && npm run test

Client

import WindowBus from "window-bus";

const iframe = document.createElement('iframe');
iframe.src = 'some_url';

iframe.onload = () => {
  const bus = new WindowBus(iframe.contentWindow, 'demo'); // demo here is the server channel
  bus.startClient(iframe.src, "optionnaly send something to server").then((whatTheServerSentInStartServer) => {

    const pre = document.body;
    const display = (res) => {
      pre.append(document.createTextNode(JSON.stringify(res)));
      pre.append(document.createElement('br'));
    }

    bus.dispatch('test', {
      somePayload: true
    }).then((res) => {
      display(res);
      return bus.dispatch('test', {
        another: 'payload'
      })
    }).then(display);

    bus.on('print', (msg) => {
      display(msg);
      return "reply from the client";
    });

    bus.dispatch('otherTest', 'hi').then((res) => {
      display(res);
      return bus.dispatch('otherTest', 'hi again')
    }).then(display);
  });
}

document.body.append(iframe);

Server (the page displayed in the iframe)

import WindowBus from "window-bus";

const bus = new WindowBus(window.parent, 'demo'); // The channel is optional, but needs to match on both sides
//const bus = new WindowBus(window.opener, 'demo'); // This will allow both popups and iframes to communicate

bus.startServer(['optional list of allowed origins'], "optionally send something to the client").then((whatTheClientSentInStartClient) => {
  const pre = document.body;
  const display = (res) => {
    pre.append(document.createTextNode(JSON.stringify(res)))
    pre.append(document.createElement('br'));
  }
  const cb = (res) => new Promise((resolve) => {
    setTimeout(() => resolve({ ...res, result1: true }), 100);
  });
  bus.on('test', cb);

  bus.on('test', (res, original) => {
    bus.off('test', cb);
    display(original);
    return { ...res, result2: true };
  });

  bus.once('otherTest', (res) => {
    setTimeout(() => {
      bus.dispatch('print', 'sent from the server').then((msg) => {
        display(msg);
      });
    }, 100);
    return res + ' for the first time';
  });
});

A note on Security

This library assumes the server is a public page and thus any client can connect to it if a CSP is not configured

Here is the header you can serve from the server to only allow https://some-client.com to connect to the server

Content-Security-Policy: frame-ancestors https://some-client.com;

You can also use the first parameter of startServer: bus.startServer(['https://some-client.com']) but the CSP is the most secure option