[Wordpress] Function create button back to top in WP admin area

//add back to top admin
if ( ! function_exists( 'enqtran_back_to_top' ) ) {
function enqtran_back_to_top() { 
    echo '<a id="backtotop" href="#" style="position: fixed;
    color: rgb(255, 255, 255);
    right: 0px;
    bottom: 5px;
    text-decoration: none;
    font-weight: bold;
    padding: 7px 5px;
    display: none;
    background: rgb(0, 115, 170);">TOP</a>';
?>
    <script>
        jQuery(window).scroll(function() {
            if(jQuery(window).scrollTop() > 500) {
                jQuery('#backtotop').show();
            } else {
                jQuery('#backtotop').hide();
            }
        });
        jQuery('#backtotop').click(function(event) {
            event.preventDefault();
            jQuery("body,html").animate({ scrollTop:0} );
        });
    </script>
<?php }
    add_action('admin_footer', 'enqtran_back_to_top');
}