Event emitter mixin

mixin.js

// -- Emitter mixin
function Emitter(base) {
  var _eventHandlers = []

  function on(eventName, callback) {
    var filter = makePattern(eventName)

    _eventHandlers.push({
      filter:   filter,
      callback: callback
    })
  }

  function off(eventName, callback) {
    var filter = makePattern(eventName)
    var index = null

    for (var i = 0, l = _eventHandlers.length; i < l; i++) {
      var ev = _eventHandlers[i]
      var sameFilter = String(filter) === String(ev.filter)
      var sameCallback = callback === ev.callback

      if (sameFilter && sameCallback) {
        index = i
        return false
      }
    })

    if (index !== null) {
      _eventHandlers.splice(index, 1)
    }
  }

  function trigger(eventName) {
    var args = [].slice.call(arguments, 1)
    args.unshift(eventName)

    console.log("trigger " + args.join(", "))

    for (var i = 0, l = _eventHandlers.length; i < l; i++) {
      var ev = _eventHandlers[i]
      if (ev.filter.test(eventName)) {
        setTimeout(function() {
          console.log("on " + eventName)
          ev.callback.apply(null, args)
        }, 0)
      }
    })
  }

  function makePattern(eventName) {
    return new RegExp("^" + eventName.replace("*", "(.*)") + "$")
  }

  base.on      = on
  base.off     = off
  base.trigger = trigger
}