work with DOM

_workWithDOM:{
      _empty: function( parent ) {
        while (parent.firstChild) {
          parent.removeChild(parent.firstChild);
        }
      },

      _removeClass: function( el, className ) {
        if( el.classList ) {
          el.classList.remove( className );
        } else {
          var classes = el.className.split(" ");
          classes.splice(classes.indexOf(className), 1);
          el.className = classes.join(' ');
        }
      },

      _addClass: function( el, className ) {
        if( el.classList ) {
          el.classList.add( className );
        } else {
          var classes = el.className.split(" ");
          el.className = classes.concat( className ).join(' ');
        }
      }
    }