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]