count the chatters & lurkers in meatspace

usercounter.js

  var UserCounter = function(activeUsers) {
    var ttl = nconf.get('ttl');

    function expiredBefore(now) {
      return function(message) {
        return message['timestamp'] + ttl > now;
      }
    }

    function update() {
      var now = new Date().getTime();
      this.activeUsers = this.activeUsers.filter(expiredBefore(now))
    }

    this.intervalId = setInterval(update.bind(this), 1000)
    this.activeUsers = activeUsers
  }

  UserCounter.prototype.message = function(userId) {
    var now = new Date().getTime(),
        message = {"id": userId, "timestamp": now};

    this.activeUsers = this.activeUsers.filter(function(msg) {
      return msg['id'] !== userId;
    }).concat([message]);
  }

  UserCounter.prototype.count = function() {
    return this.activeUsers.length;
  }

  var userCounter = new UserCounter([]);