This code not work,

Code:
if( document.body.scrollTop() > 200 ) {
$( '.navigation' ).addClass( 'fixed' );
} else {
$( '.navigation' ).removeClass( 'fixed' );
}
I want it to work without jQuery, because half my site die's when i use jQuery, jsut want a simple scrollTop script for when im 200px from top it locks navigation fixed top the top, it works with jQuery but not without and been trying for hours to get it to work, any help would be kindly recieve thanks.