code: function(el) {
        if (!el) {
      		return this[0] ? this.first().prevAll().length : -1;
      	}
      	if (''+el === el) {
      		return u.toArray(u(el)).indexOf(this[0]);
      	}
        el = el.ujs ? el[0] : el;
      	return u.toArray(this).indexOf(el);
      }
docs: index method
  get the index of an element
  @param  {object|string} [el] - elements or css selector
  @return {number}               index