Remove all classes except for the ones given.

jQuery.removeClassExcept.js

/*! (c) 2015 John Przeslakowski | Code released under the MIT license | goodpixels.co.uk */

( function ( $ ) {

	$.fn.removeClassExcept = function ( val ) {

		return this.each( function( index, el ) {
			
			var keep = val.split( ' ' );
			var reAdd = [];
			var $el = $(el);
		
			for( var c = 0; c < keep.length; c++ ) {

				if( $el.hasClass( keep[ c ] ) ) reAdd.push( keep[ c ] );

			}
		
			$el.removeClass().addClass( reAdd.join( ' ' ) );
		
		} );

	};

}( jQuery ) );