code: function removeClass( element ) {
    const removeClassNamesArray = _sliceArgs( arguments );
    if ( hasClassList ) {
      element.classList.remove
      .apply( element.classList, removeClassNamesArray );
    } else {
      var classes = element.className.split( ' ' );
      removeClassNamesArray.forEach( function( className ) {
        if ( className ) {
          classes.splice( classes.indexOf( className ), 1 );
        }
      } );
      element.className = classes.join( ' ' );
    }
  }
docs: Remove CSS class from an element.
  
  @param {HTMLNode} element - A DOM element.
  @param {string} className - CSS selector.