<i onclick="void showhide(this.parentNode)" class="fa fa-plus">

function showhide(e) {
   if(e.childNodes[5].className=='') {
      e.childNodes[5].className='someclass';
      alert(e.childNodes[5].className);
   }else{
      e.childNodes[5].className='';
      alert(e.childNodes[5].className);
   }

}

function showhide(e) {
     e.children[5].classList.toggle('someclass')
}