MediaWiki:Gadget-SidebarTOC.js

$(function(){
    if (!$('#toc').length) {
        return;
    }
    var i18n = {
        header: 'Contents',
        top: '(Top)'
    };

    // Hide the existing TOC
    $('#toc').hide();
    
    new ResizeObserver(function(entries) {
		if (window.innerWidth <= 720) {
			$('#mw-panel').css('height', '');
		}
		else {
			$('#mw-panel').css('height', document.body.scrollHeight - 10);
		}
	}).observe($('#content')[0]);
	var tocCollapsed = (localStorage.getItem("sidebar_vector_c_p-toc") !== "n");
	$('<nav id="p-toc" class="vector-menu mw-portlet mw-portlet-toc vector-menu-portal portal" aria-labelledby="p-toc-label" role="navigation">').append(
	    $('<h3 id="p-toc-label" class="vector-menu-heading" tabindex="0">').append(
	        $('<span class="vector-menu-heading-label">').text(i18n.header)
	    ).on("keypress", function(event) {
			if (event.which == 13) {
				$(this).trigger("click");
				event.stopImmediatePropagation()
			}
		}).on("click", function(event) {
    var $el = $(this).parent();
    event.stopPropagation();

    if ($el.hasClass("collapsed")) {
        localStorage.setItem("sidebar_vector_c_p-toc", "n");
        $el.find(".vector-menu-content").slideDown("fast");
        $el.removeClass("collapsed").addClass("expanded");
    } else {
        localStorage.setItem("sidebar_vector_c_p-toc", "y");
        $el.find(".vector-menu-content").slideUp("fast");
        $el.removeClass("expanded").addClass("collapsed");
    }
}),
	    $('<div class="vector-menu-content">').append(
	        $('<ul class="vector-menu-content-list">').append(
	        	$('<li class="toclevel-1 tocsection-0">').append($('<a href="#">').append(
	        		$('<span class="toctext">').text(i18n.top)
	        	)),
	            $('#toc > ul').children().clone()
	        )
	    ).addClass($('#toc').parent().prop('class').split(/\s+/).filter(function(classname) {
	    	return classname.startsWith('toc-');
	    }).join(' ')).css('display', tocCollapsed ? 'none' : '')
	).addClass(tocCollapsed ? 'collapsed' : '').appendTo('#mw-panel');

	// Add scroll event to highlight current section
$(window).on('scroll', function() {
    var scrollPosition = $(this).scrollTop();
    var currentSection;

    // Find the current section based on scroll position
    $('.mw-headline').each(function() {
        if ($(this).offset().top <= scrollPosition) {
            currentSection = $(this);
        } else {
            return false;
        }
    });

    // Remove existing tocsection-current class and add it to the current section
    $('#p-toc .tocsection-current').removeClass('tocsection-current');
    if (currentSection) {
        $('#p-toc a[href="#' + currentSection.attr('id') + '"]').closest('li').addClass('tocsection-current');
    }
});
});