lastSortOrder : undefined,
dataUnsorted : undefined

var currSortOrder = this.options.sortOrder,
      lastSortOrder = this.options.lastSortOrder;

if(lastSortOrder === undefined && this.options.dataUnsorted === undefined){
  this.options.dataUnsorted = this.options.data.slice();
} else if(lastSortOrder === 'asc' && currSortOrder === 'desc'){
   this.options.sortOrder     = 'asc';
   this.options.sortName      = undefined;
   this.options.lastSortOrder = undefined;
   this.options.data          = this.options.dataUnsorted.slice();
   this.data                  = this.options.data;
   this.options.dataUnsorted  = undefined;
     return;
}

if(!(lastSortOrder === undefined && currSortOrder === 'asc'))
   this.options.lastSortOrder = currSortOrder;

if (this.options.sortName === $this.data('field')) { 
   this.options.sortOrder = this.options.sortOrder === 'asc' ? 'desc' : 'asc';
} else {
   this.options.sortName = $this.data('field');

   if(this.options.lastSortOrder === undefined)
      #this.options.sortOrder = 'desc';
  else
      this.options.sortOrder = $this.data('order') === 'asc' ? 'desc' : 'asc';
}