JavaScript Automation in OS X Yosemite

js_osa_test.js

var Mail = Application('Mail')
  , matches
  , pad;

pad = function (input, length, fill) {
  if (!fill || fill.length > 1) {
    fill = (typeof input === 'string') ? ' ' : '0';
  }
  input = String(input);
  return (
    input.length >= length
    ? input
    : new Array(length - input.length + 1).join(fill) + input
  );
}

matches = Mail.inbox.messages.whose({subject: {_contains: 'Friday'}})();

matches.forEach(function (message) {
  var date = message.dateReceived()
    , dateString = date.getFullYear() + '-' + pad(date.getMonth() + 1, 2) + '-' + pad(date.getDate(), 2);
  console.log(dateString + ' ' + message.subject());
});

This gets every message from your inbox(es) in Mail with a subject that contains the word "Friday", and prints them in the "Messages" pane at the bottom of the Script Editor window.

The correct extension for OSA (Open Scripting Architecture) scripts is .scpt, but GitHub keeps changing it back to AppleScript when I set it to JavaScript, so I gave up and renamed it .js. Either way, you can just copy and paste this into the Script Editor app in OS X (requires Yosemite) and try it out for yourself.

Some basic info here:
https://developer.apple.com/library/mac/releasenotes/InterapplicationCommunication/RN-JavaScriptForAutomation/

WWDC 2014 session:
https://developer.apple.com/videos/wwdc/2014/?id=306