In this example ignite.js is used to build a RSS feed reader. The state machine periodically requests the RSS feed xml, parses it and emits events containing any new items found in the feed data.

The four states in the machine, Regulate, Request, ParseXml and Broadcast form a loop. The Request state requests the xml, and on response, passes the data to the ParseXml state, where it is parsed.

From here the machine transitions to the Broadcast state. This state has its own closure where it maintains a record of the build date from the last feed passed to it (lastBuildDate). The state can then tell if it has already been presented with any given feed it receives. If a feed is new, its items are inspected and any new items accumulated in an array (newFeeds). The machine then emits an event called 'rssFeed' containing the array.

The last step in the loop is the Regulate state. This state is used to regulate the frequency of the loop. The timeout plug-in is used to produce an event called 'timeout' after a specified number of milliseconds (refresh). On receipt of the event, the machine transitions to Read for another loop. Note, the regulation produced by the Regulate state is crude and only guarantees that the time taken for each loop is greater than the time spent waiting.

var _ = require('underscore'),
    xml2js = require('xml2js');

function rssFeed (fire, url, refresh) {
  var parser;

  this.startState = 'Init';
  this.states = {
    Init: {
      entry: function () {
        parser = new xml2js.Parser();
        fire.$regEmitter('parser', parser, true);
        return 'Request';
      }
    },

    Regulate: {
      timeout: refresh,
      actions: {
        'timeout': 'Request'
      }
    },

    Request: {
      async: {
        fn: 'request',
        fnArgs: [ { uri: url } ]
      },
      actions: {
        '.done': 'ParseXml'
      }
    },

    ParseXml: function () {
      var sax;
      return {
        entry: function (response, body) {
          sax = parser.parseString(body);
        },
        actions: {
          '.end': function (xml) {
            sax.close();
            return [ 'Broadcast', xml.channel ];
          }
        }
      };
    },

    Broadcast: function () {
      var lastBuildDate = new Date(0, 0, 0);
      return {
        guard: function (channel) {
          channel.lastBuildDate = new Date(channel.lastBuildDate);
          if (channel.lastBuildDate <= lastBuildDate) {
            return 'Regulate';
          }
        },
        work: function (channel) {
          var newFeeds = _.select(channel.item, function (item) {            
            item.pubDate = new Date(item.pubDate);
            return item.pubDate > lastBuildDate;
          });
          lastBuildDate = channel.lastBuildDate;

          if (!_.isEmpty(newFeeds)) {
            fire.$event('rssFeed', newFeeds);
          }
          return 'done';
        },
        actions: {
          '.done': 'Regulate'
        }
      };
    }

  };

  this.defaults = {
    actions: {
      '.err': '@error',
      'api.stop': '@exit'
    }
  };
};

rssFeed.api = [ 'stop' ];
rssFeed.defaults = {
  imports: { 
    request: require('request')
  },
  args: [ 'http://mf.feeds.reuters.com/reuters/UKTopNews', 5000 ]
};
rssFeed.runner = {
  on: {
    'rssFeed': function (newFeeds) {
      _.each(newFeeds, function (feed) {
        console.log('%s %s', feed.pubDate.toLocaleTimeString(), feed.title);
      });
    }
  }
};

module.exports = rssFeed;

 $ ./bin/ignite examples/rss_feed.js
 Running examples/rss_feed.js
 12:10:06: Second NATO helicopter crashes; Afghans protest over killings
 12:06:58: Washington convinces Saleh not to return to Yemen: report
 12:00:44: Stocks hit by U.S. unease as ECB supports Italy, Spain
 11:46:49: Syrian tanks pound city, Saudi king condemns violence
 10:55:44: Britain, other eurozone countries face ratings cut - Jim Rogers
 10:54:15: Wall Street braces for impact from U.S. downgrade
 09:14:03: ECB backs Italy, Spain as policymakers pledge action
 08:34:04: Police arrest 100 after riots in London
 08:31:49: Euro zone must ensure financial stability - Osborne
 _