https://michielburger.nl/ndxzsite/js/jquery.ndxz_expander.js?v=2.0

1/*
2The original expanding menu was created by Ross Cairns.
3Much thanks to him for creating something that became so useful.
4
5This version of expanding is suited to be used with Indexhibit v0.9....and greater.
6
7Vaska / Indexhibit.org
8*/
9
10(function($){
11$.fn.ndxzExpander = function(options) 
12{   
13    var options = $.extend({
14		active: 		"", 
15		speed:          100, // speed of transitions
16		single:       	true, // only allow one node open at a time
17		_identifier: $(this)
18	}, options);
19	
20	//var exclude = new Array();
21	//exclude[0] = 'section_4';
22	
23	$.fn.ndxzExpander.init = function()
24	{
25		// let's add a feature to ignore certain sections altogether
26		// need to use each for this then
27		$('ul.section').each(function()
28		{
29			//if (jQuery.inArray(this.id, exclude))
30			//{
31				
32				//alert( '#menu ul#' + this.id + ' span.section_title' );
33				// need to rewrite the expander links
34				$('#menu ul#' + this.id + ' li a span.section_title').unwrap();
35				$('#menu ul#' + this.id + ' li span.section_title').next().hide();
36				$('#menu ul#' + this.id + ' li span.subsection_title').next().hide();
37				$('#menu ul#' + this.id + ' span.section_title').bind('click', function(){ $.fn.ndxzExpander.expander(this); return false; });
38				$('#menu ul#' + this.id + ' span.subsection_title').bind('click', function(){ $.fn.ndxzExpander.expander(this); return false; });
39			//}
40		});
41
42		// show active
43		$.fn.ndxzExpander.active();
44	}
45	
46	/*
47	<ul class='section active_section' id='section_2'>
48	<li id='section_title_2'>
49	<a href='http://www.indexhibit.dev/project/'><span id='section_link_2' class='section_title active'>Projects</span></a>
50	*/
51	
52	$.fn.ndxzExpander.active = function()
53	{
54		//$('#menu ul.active_section li a span.active').nextAll('ul').toggle(options.speed);
55		
56		// open up the pathway
57		// works with active pages - but not section tops...
58		$('li.active').parents('ul').show();
59		
60		// let's register the active ul - messy
61		var a = new Array(); var b;
62		//a = $('span.active').parents('ul').map(function () { return this.id; }).get().reverse();
63		a = $('li.active').parents('ul').map(function () { return this.id; }).get().reverse();
64		
65		// if there is no active link at all
66		// review this later...
67		if (a == '')
68		{
69			// maybe we need to look/expand for an active section instead?
70			$('ul.active_section li ul.sub_section').show();
71			return false;
72		}
73		else
74		{
75			b = a[0];
76			b = b.replace('section_', '');
77			b = 'section_link_' + b;
78		}
79		
80		options.active = b;
81	}
82
83	$.fn.ndxzExpander.expander = function(obj)
84	{
85		// nothing if it's the active part
86		if (options.active == obj.id) return false;
87
88		// we need to make sure it's not themselves
89		if (options.single == true)
90		{
91			// this works but not with sub section clicks
92			if ($('span#' + obj.id).hasClass('subsection_title'))
93			{
94				var tmp = obj.id;
95				tmp = tmp.split('_');
96				var subsection = tmp.pop();
97				var section = tmp.pop();
98				
99				$('ul#section_' + section + ' ul.subsection:visible').hide(options.speed);
100				
101				// register the new active part
102				options.active = 'section_link_' + section;
103			}
104			else
105			{
106				$('#menu ul li span.section_title').next().hide(options.speed);
107				
108				// register the new active part
109				options.active = obj.id;
110			}
111		}
112
113		var found = $('span#' + obj.id).parent().find('ul').length;
114
115		if (found > 0)
116		{
117			// show all secondary
118			$('span#' + obj.id).nextAll('ul').toggle(options.speed);
119		}
120		else
121		{
122			$('span#' + obj.id  + ' + ul').toggle(options.speed);
123		}
124	}
125	
126	// Initalize the expander
127	$.fn.ndxzExpander.init(this);
128};
129})(jQuery);