polyfill.js

;(function (global) {

  if ("EventSource" in global) return;

  var reTrim = /^(\s|\u00A0)+|(\s|\u00A0)+$/g;

  var EventSource = function (url) {
    var eventsource = this,
      interval = 500, // polling interval
      lastEventId = null,
      cache = '';

    if (!url || typeof url != 'string') {
      throw new SyntaxError('Not enough arguments');
    }

    this.URL = url;
    this.readyState = this.CONNECTING;
    this._pollTimer = null;
    this._xhr = null;

    function pollAgain(interval) {
      eventsource._pollTimer = setTimeout(function () {
        poll.call(eventsource);
      }, interval);
    }

    function poll() {
      try { // force hiding of the error message... insane?
        if (eventsource.readyState == eventsource.CLOSED) return;

        // NOTE: IE7 and upwards support
        var xhr = new XMLHttpRequest();
        xhr.open('GET', eventsource.URL, true);
        xhr.setRequestHeader('Accept', 'text/event-stream');
        xhr.setRequestHeader('Cache-Control', 'no-cache');
        // we must make use of this on the server side if we're working with Android - because they don't trigger
        // readychange until the server connection is closed
        xhr.setRequestHeader('X-Requested-With', 'XMLHttpRequest');

        if (lastEventId != null) xhr.setRequestHeader('Last-Event-ID', lastEventId);
        cache = '';

        xhr.timeout = 50000;
        xhr.onreadystatechange = function () {
          if (this.readyState == 3 || (this.readyState == 4 && this.status == 200)) {
            // on success
            if (eventsource.readyState == eventsource.CONNECTING) {
              eventsource.readyState = eventsource.OPEN;
              eventsource.dispatchEvent('open', { type: 'open' });
            }

            var responseText = '';
            try {
              responseText = this.responseText || '';
            } catch (e) {}

            // process this.responseText
            var parts = responseText.substr(cache.length).split("\n"),
              eventType = 'message',
              data = [],
              i = 0,
              line = '';

            cache = responseText;

            // TODO handle 'event' (for buffer name), retry
            for (; i < parts.length; i++) {
              line = parts[i].replace(reTrim, '');
              if (line.indexOf('event') == 0) {
                eventType = line.replace(/event:?\s*/, '');
              } else if (line.indexOf('retry') == 0) {
                var retry = parseInt(line.replace(/retry:?\s*/, ''));
                if(!isNaN(retry)) { interval = retry; }
              } else if (line.indexOf('data') == 0) {
                data.push(line.replace(/data:?\s*/, ''));
              } else if (line.indexOf('id:') == 0) {
                lastEventId = line.replace(/id:?\s*/, '');
              } else if (line.indexOf('id') == 0) { // this resets the id
                lastEventId = null;
              } else if (line == '') {
                if (data.length) {
                  var event = new MessageEvent(data.join('\n'), eventsource.url, lastEventId);
                  eventsource.dispatchEvent(eventType, event);
                  data = [];
                  eventType = 'message';
                }
              }
            }

            if (this.readyState == 4) pollAgain(interval);
            // don't need to poll again, because we're long-loading
          } else if (eventsource.readyState !== eventsource.CLOSED) {
            if (this.readyState == 4) { // and some other status
              // dispatch error
              eventsource.readyState = eventsource.CONNECTING;
              eventsource.dispatchEvent('error', { type: 'error' });
              pollAgain(interval);
            } else if (this.readyState == 0) { // likely aborted
              pollAgain(interval);
            } else {
            }
          }
        };

        xhr.send();

        setTimeout(function () {
          if (true || xhr.readyState == 3) xhr.abort();
        }, xhr.timeout);

        eventsource._xhr = xhr;

      } catch (e) { // in an attempt to silence the errors
        eventsource.dispatchEvent('error', { type: 'error', data: e.message }); // ???
      }
    };

    poll(); // init now
  };

  EventSource.prototype = {
    close: function () {
      // closes the connection - disabling the polling
      this.readyState = this.CLOSED;
      clearInterval(this._pollTimer);
      this._xhr.abort();
    },
    CONNECTING: 0,
    OPEN: 1,
    CLOSED: 2,
    dispatchEvent: function (type, event) {
      var handlers = this['_' + type + 'Handlers'];
      if (handlers) {
        for (var i = 0; i < handlers.length; i++) {
          handlers[i].call(this, event);
        }
      }

      if (this['on' + type]) {
        this['on' + type].call(this, event);
      }
    },
    addEventListener: function (type, handler) {
      if (!this['_' + type + 'Handlers']) {
        this['_' + type + 'Handlers'] = [];
      }

      this['_' + type + 'Handlers'].push(handler);
    },
    removeEventListener: function (type, handler) {
      var handlers = this['_' + type + 'Handlers'];
      if (!handlers) {
        return;
      }
      for (var i = handlers.length - 1; i >= 0; --i) {
        if (handlers[i] === handler) {
          handlers.splice(i, 1);
          break;
        }
      }
    },
    onerror: null,
    onmessage: null,
    onopen: null,
    readyState: 0,
    URL: ''
  };

  var MessageEvent = function (data, origin, lastEventId) {
    this.data = data;
    this.origin = origin;
    this.lastEventId = lastEventId || '';
  };

  MessageEvent.prototype = {
    data: null,
    type: 'message',
    lastEventId: '',
    origin: ''
  };

  if ('module' in global) module.exports = EventSource;
  global.EventSource = EventSource;

})(this);