Use this :
  $("#element id").removeClass();
Calling removeClass with no parameters will remove all of the item’s classes.
You can also use (but is not necessarily recommended, the correct way is the one above):
      $("#element id").removeAttr('class');
      $("#element id").attr('class', '');
      $('#element id')[0].className="";
If you didn’t want to use jquery you can use java script:
    document.getElementById('item').className="";
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solved How to deactivate a class using jquery [closed]