https://www.archives.gov/sites/all/themes/nara/assets/javascripts/bootstrap/scrollspy.js?tm7hkg

1/* ========================================================================
2 * Bootstrap: scrollspy.js v3.2.0
3 * http://getbootstrap.com/javascript/#scrollspy
4 * ========================================================================
5 * Copyright 2011-2014 Twitter, Inc.
6 * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
7 * ======================================================================== */
8
9
10+function ($) {
11  'use strict';
12
13  // SCROLLSPY CLASS DEFINITION
14  // ==========================
15
16  function ScrollSpy(element, options) {
17    var process  = $.proxy(this.process, this)
18
19    this.$body          = $('body')
20    this.$scrollElement = $(element).is('body') ? $(window) : $(element)
21    this.options        = $.extend({}, ScrollSpy.DEFAULTS, options)
22    this.selector       = (this.options.target || '') + ' .nav li > a'
23    this.offsets        = []
24    this.targets        = []
25    this.activeTarget   = null
26    this.scrollHeight   = 0
27
28    this.$scrollElement.on('scroll.bs.scrollspy', process)
29    this.refresh()
30    this.process()
31  }
32
33  ScrollSpy.VERSION  = '3.2.0'
34
35  ScrollSpy.DEFAULTS = {
36    offset: 10
37  }
38
39  ScrollSpy.prototype.getScrollHeight = function () {
40    return this.$scrollElement[0].scrollHeight || Math.max(this.$body[0].scrollHeight, document.documentElement.scrollHeight)
41  }
42
43  ScrollSpy.prototype.refresh = function () {
44    var offsetMethod = 'offset'
45    var offsetBase   = 0
46
47    if (!$.isWindow(this.$scrollElement[0])) {
48      offsetMethod = 'position'
49      offsetBase   = this.$scrollElement.scrollTop()
50    }
51
52    this.offsets = []
53    this.targets = []
54    this.scrollHeight = this.getScrollHeight()
55
56    var self     = this
57
58    this.$body
59      .find(this.selector)
60      .map(function () {
61        var $el   = $(this)
62        var href  = $el.data('target') || $el.attr('href')
63        var $href = /^#./.test(href) && $(href)
64
65        return ($href
66          && $href.length
67          && $href.is(':visible')
68          && [[$href[offsetMethod]().top + offsetBase, href]]) || null
69      })
70      .sort(function (a, b) { return a[0] - b[0] })
71      .each(function () {
72        self.offsets.push(this[0])
73        self.targets.push(this[1])
74      })
75  }
76
77  ScrollSpy.prototype.process = function () {
78    var scrollTop    = this.$scrollElement.scrollTop() + this.options.offset
79    var scrollHeight = this.getScrollHeight()
80    var maxScroll    = this.options.offset + scrollHeight - this.$scrollElement.height()
81    var offsets      = this.offsets
82    var targets      = this.targets
83    var activeTarget = this.activeTarget
84    var i
85
86    if (this.scrollHeight != scrollHeight) {
87      this.refresh()
88    }
89
90    if (scrollTop >= maxScroll) {
91      return activeTarget != (i = targets[targets.length - 1]) && this.activate(i)
92    }
93
94    if (activeTarget && scrollTop <= offsets[0]) {
95      return activeTarget != (i = targets[0]) && this.activate(i)
96    }
97
98    for (i = offsets.length; i--;) {
99      activeTarget != targets[i]
100        && scrollTop >= offsets[i]
101        && (!offsets[i + 1] || scrollTop <= offsets[i + 1])
102        && this.activate(targets[i])
103    }
104  }
105
106  ScrollSpy.prototype.activate = function (target) {
107    this.activeTarget = target
108
109    $(this.selector)
110      .parentsUntil(this.options.target, '.active')
111      .removeClass('active')
112
113    var selector = this.selector +
114        '[data-target="' + target + '"],' +
115        this.selector + '[href="' + target + '"]'
116
117    var active = $(selector)
118      .parents('li')
119      .addClass('active')
120
121    if (active.parent('.dropdown-menu').length) {
122      active = active
123        .closest('li.dropdown')
124        .addClass('active')
125    }
126
127    active.trigger('activate.bs.scrollspy')
128  }
129
130
131  // SCROLLSPY PLUGIN DEFINITION
132  // ===========================
133
134  function Plugin(option) {
135    return this.each(function () {
136      var $this   = $(this)
137      var data    = $this.data('bs.scrollspy')
138      var options = typeof option == 'object' && option
139
140      if (!data) $this.data('bs.scrollspy', (data = new ScrollSpy(this, options)))
141      if (typeof option == 'string') data[option]()
142    })
143  }
144
145  var old = $.fn.scrollspy
146
147  $.fn.scrollspy             = Plugin
148  $.fn.scrollspy.Constructor = ScrollSpy
149
150
151  // SCROLLSPY NO CONFLICT
152  // =====================
153
154  $.fn.scrollspy.noConflict = function () {
155    $.fn.scrollspy = old
156    return this
157  }
158
159
160  // SCROLLSPY DATA-API
161  // ==================
162
163  $(window).on('load.bs.scrollspy.data-api', function () {
164    $('[data-spy="scroll"]').each(function () {
165      var $spy = $(this)
166      Plugin.call($spy, $spy.data())
167    })
168  })
169
170}(jQuery);