MediaWiki:Gadget-SidebarTOC.js

function customizeToC() {
    var $toc = $( '#toc' );

    if ( !$toc.length ) {
        return;
    }

    var $mwContent = $( '#mw-content-text' );
    var $floatTOC = $toc
        .clone()
        .removeAttr( 'id' )
        .addClass( 'floatTOC' )
        .appendTo( $mwContent )
        .css( {
            height: $mwContent.height(), // Set ToC height to match article height
            overflowY: 'auto' // Enable vertical scrolling if ToC exceeds article height
        } );

    // Update scrollHandler function to use $mwContent instead of window
    var scrollHandler = function () {
        var scrollTop = $mwContent.scrollTop(); // Use scrollTop of $mwContent

        if ( scrollTop > 0 ) { // Adjust condition based on scroll position
            $floatTOC.css( 'visibility', 'visible' );
        } else {
            $floatTOC.css( 'visibility', 'hidden' );
        }
    };

    // Update event binding to use $mwContent instead of window
    $mwContent.on( 'scroll', $.throttle( 250, scrollHandler ) );
}

// Call the customizeToC function when jQuery and its dependencies are ready
mw.loader.using( ['jquery', 'jquery.throttle-debounce'], customizeToC );