docs: function InputHasChanged ($el) {
      if (!(this instanceof InputHasChanged)) return new InputHasChanged($el);
  
      var me = this;
  
      this.original = $el.value;
  
      function handler (e) {
          if (_filter.indexOf(e.keyCode) > -1) return;
  
          var val = $el.value;
  
          if (val !== me.original) {
              me.emit('changed', val);
          } else {
              me.emit('original', val);
          }
      }
  
      dom.on($el, 'keyup', handler);
  }