src/js/assets/selectr/selectr.js
function(event, func) {
    this._events = this._events || {};
    this._events[event] = this._events[event] || [];
    this._events[event].push(func);
  }
function(event, func) {
    this._events = this._events || {};
    this._events[event] = this._events[event] || [];
    this._events[event].push(func);
  }
Add custom event listener
@param  {String} event Event type
@param  {Function} func   Callback
@return {Void}