self-addressed

Transform postMessage calls to return a promise

Available on NPM and bower under name self-addressed.

Provides single function stamp(mailman, address, data), that returns a Promise.

Example

var stamp = require('self-addressed');
var mailman = function (address, envelope) {
    address.postMessage(envelope, '*');
};
stamp(mailman, window, { foo: 'foo' })
    .then(function (response) {
        console.log('got response to our letter', response);
    });

Api

Single function selfAddressed can do 3 things at once

• selfAddressed(mailman, address, data) - can deliver data via mailman to address and then returns a promise that resolves with response.
• selfAddressed(envelope, letter) - puts letter into valid enveloper to be delivered back as a response.
• selfAddressed(envelope) - returns either the letter stored in the envelope or undefined if this is an invalid envelope.

Extras

You can see verbose log messages by setting selfAddressed.options.verbose = true;

Typical workflow

iframed page.html that wants to communicate with the parent can postMessage and receive a reply

function mailman(address, msg) {
  address.postMessage(msg, '*');
}
window.onmessage = function (event) {
  selfAddressed(event.data);
};
selfAddressed(mailman, parent, 'foo')
  .then(function (response) {
    console.log(response); // "bar"
  });

index page that iframes page.html inside and uses onmessage to open the envelope, place new letter inside and send the response back to the source.

function mailman(address, msg) {
  address.postMessage(msg, '*');
}
window.onmessage = function (event) {
  var letter = selfAddressed(event.data);
  // if letter === undefined => not an envelope, handle differently!
  var returnAddress = event.source;
  selfAddressed(event.data, 'bar'); // places the letter into the same envelope
  selfAddressed(mailman, returnAddress, event.data);
};

Combined with other data

Often we have other sources of data to be handled inside onmessage callback. One can ask if the received data is self-addressed to determine if it has been handled by self-addressed or not using selfAddressed.is(envelope).

window.onmessage = function (event) {
  // event could be self-addressed envelope or not
  if (selfAddressed.is(event.data)) {
    var letter = selfAddressed(event.data);
    if (!letter) {
      // nothing to do - it has been handled via promise resolution
    } else {
      // handle letter, maybe reseal and send response?
    }
  } else {
    // not an envelope - handle yourself
  }
}

Small print

Author: Gleb Bahmutov © 2015

• @bahmutov
• glebbahmutov.com
• blog

License: MIT - do anything with the code, but don't blame me if it does not work.

Spread the word: tweet, star on github, etc.

Support: if you find any problems with this module, email / tweet / open issue on Github

MIT License

Copyright (c) 2015 Gleb Bahmutov

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.