undefined' is not a function (evaluating '$('#pf-article')')

undefined' is not a function (evaluating '$('#pf-article')')

I am trying to hide an element if another one exists

  1. $(document).ready(function(){
  2. var pf  = $('#pf-box').length;
  3. if (pf != 0) { 
  4. $('#toTop').hide;
  5. }
  6. });
I get the error :
undefined' is not a function (evaluating '$('#pf-article')')

and of course there is an element id="pf-box"  in my page


thanks for helping