A simple event emitter mixin modified a bit from seajs

event-emitter.js

/*
 * EventEmitter from seajs
 */
var EventEmitter = {
  // Bind event
  on: function(name, callback) {
    var events = this.events
    var list = events[name] || (events[name] = [])
    list.push(callback)
    return this
  },

  // Remove event. If `callback` is undefined, remove all callbacks for the
  // event. If `event` and `callback` are both undefined, remove all callbacks
  // for all events
  off: function(name, callback) {
    // Remove *all* events
    if (!(name || callback)) {
      this.events = {}
      return this
    }

    var events = this.events
    var list = events[name]
    if (list) {
      if (callback) {
        for (var i = list.length - 1; i >= 0; i--) {
          if (list[i] === callback) {
            list.splice(i, 1)
          }
        }
      }
      else {
        delete events[name]
      }
    }

    return this
  },

  // Emit event, firing all bound callbacks. Callbacks receive the same
  // arguments as `emit` does, apart from the event name
  emit: function(name, data) {
    var list = this.events[name]

    if (list) {
      // Copy callback lists to prevent modification
      list = list.slice()

      // Execute event callbacks, use index because it's the faster.
      for(var i = 0, len = list.length; i < len; i++) {
        list[i](data)
      }
    }

    return this
  }
}

原本抄到 oceanify/import.js 里了，现在发现用不到了，拷出来放在这里，方便以后用