<div id="selector" class="navbar navbar-default"> 
<ul class="nav navbar-nav"> 
<li><a href="#one">one</a> </li> 
<li><a href="#two">two</a> </li> 
<li><a href="#three">three</a> </li> 
</ul>
</div>
<div data-spy="scroll" data-target="#selector" style="height:100px; overflow:hidden;overflow-y: auto;" > 
<h4 id="one" >ibe</h4><p>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/></p> 
<h4 id="two" >two</h4><p>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/></p> 
<h4 id="three" >three</h4><p>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/>One的具体内容<br/></p>
</div>

function ScrollSpy(element, options) {
  this.$body     = $(document.body)
  this.$scrollElement = $(element).is(document.body) "htmlcode">

ScrollSpy.prototype.refresh = function () {
  var that     = this
  var offsetMethod = 'offset'
  var offsetBase  = 0

  this.offsets   = []
  this.targets   = []
  this.scrollHeight = this.getScrollHeight()

  if (!$.isWindow(this.$scrollElement[0])) {
   offsetMethod = 'position'
   offsetBase  = this.$scrollElement.scrollTop()
  }

  this.$body
   .find(this.selector)
   .map(function () {
    var $el  = $(this)
    var href = $el.data('target') || $el.attr('href')
    var $href = /^#./.test(href) && $(href)
    
    return ($href
     && $href.length
     && $href.is(':visible')
     && [[$href[offsetMethod]().top + offsetBase, href]]) || null
   })
   .sort(function (a, b) { return a[0] - b[0] })
   .each(function () {
    that.offsets.push(this[0])
    that.targets.push(this[1])
   })

 }




它主要实现了什么呢？
1.默认用offset来获取定位值，如果滚动区域不是window则用position来获取


if (!$.isWindow(this.$scrollElement[0])) {
   offsetMethod = 'position'
   offsetBase  = this.$scrollElement.scrollTop()
  }



2.根据导航上的hashkey来遍历获取 滚动区域内的hashkey对应的offset值：


this.$body
   .find(this.selector)
   .map(function () {
    var $el  = $(this)
    var href = $el.data('target') || $el.attr('href')
    var $href = /^#./.test(href) && $(href)
    
    return ($href
     && $href.length
     && $href.is(':visible')
     && [[$href[offsetMethod]().top + offsetBase, href]]) || null
   })
   .sort(function (a, b) { return a[0] - b[0] })
   .each(function () {
    that.offsets.push(this[0])
    that.targets.push(this[1])
   })



process方法


滚动条事件触发函数，用于计算当前需要高亮那个导航菜单


ScrollSpy.prototype.process = function () {
  var scrollTop  = this.$scrollElement.scrollTop() + this.options.offset
  var scrollHeight = this.getScrollHeight()
  var maxScroll  = this.options.offset + scrollHeight - this.$scrollElement.height()
  var offsets   = this.offsets
  var targets   = this.targets
  var activeTarget = this.activeTarget
  var i

  if (this.scrollHeight != scrollHeight) {
   this.refresh()
  }

  if (scrollTop >= maxScroll) {
   return activeTarget != (i = targets[targets.length - 1]) && this.activate(i)
  }

  if (activeTarget && scrollTop < offsets[0]) {
   this.activeTarget = null
   return this.clear()
  }

  for (i = offsets.length; i--;) {
   activeTarget != targets[i]
    && scrollTop >= offsets[i]
    && (offsets[i + 1] === undefined || scrollTop < offsets[i + 1])
    && this.activate(targets[i])
  }
 }




主要作用：
1.获取滚动容器已滚动距离：


var scrollTop  = this.$scrollElement.scrollTop() + this.options.offset



2.滚动容器可以滚动的最大高度:


var maxScroll  = this.options.offset + scrollHeight - this.$scrollElement.height()



3.设置滚动元素逻辑，给当前匹配元素添加高亮：


for (i = offsets.length; i--;) {
   activeTarget != targets[i]
    && scrollTop >= offsets[i]
    && (offsets[i + 1] === undefined || scrollTop < offsets[i + 1])
    && this.activate(targets[i])
  }



active方法


设置指定的导航菜单高亮


ScrollSpy.prototype.activate = function (target) {
  this.activeTarget = target

  this.clear()

  var selector = this.selector +
   '[data-target="' + target + '"],' +
   this.selector + '[href="' + target + '" rel="external nofollow" rel="external nofollow" ]'

  var active = $(selector)
   .parents('li')
   .addClass('active')

  if (active.parent('.dropdown-menu').length) {
   active = active
    .closest('li.dropdown')
    .addClass('active')
  }

  active.trigger('activate.bs.scrollspy')
 }



clear方法


清除所有高亮菜单


ScrollSpy.prototype.clear = function () {
  $(this.selector)
   .parentsUntil(this.options.target, '.active')
   .removeClass('active')
 }



 源码




+function ($) {
 'use strict';

 // SCROLLSPY CLASS DEFINITION
 // ==========================

 function ScrollSpy(element, options) {
  this.$body     = $(document.body)
  this.$scrollElement = $(element).is(document.body) "' + target + '"],' +
   this.selector + '[href="' + target + '" rel="external nofollow" rel="external nofollow" ]'

  var active = $(selector)
   .parents('li')
   .addClass('active')

  if (active.parent('.dropdown-menu').length) {
   active = active
    .closest('li.dropdown')
    .addClass('active')
  }

  active.trigger('activate.bs.scrollspy')
 }

 ScrollSpy.prototype.clear = function () {
  $(this.selector)
   .parentsUntil(this.options.target, '.active')
   .removeClass('active')
 }


 // SCROLLSPY PLUGIN DEFINITION
 // ===========================

 function Plugin(option) {
  return this.each(function () {
   var $this  = $(this)
   var data  = $this.data('bs.scrollspy')
   var options = typeof option == 'object' && option

   if (!data) $this.data('bs.scrollspy', (data = new ScrollSpy(this, options)))
   if (typeof option == 'string') data[option]()
  })
 }

 var old = $.fn.scrollspy

 $.fn.scrollspy       = Plugin
 $.fn.scrollspy.Constructor = ScrollSpy


 // SCROLLSPY NO CONFLICT
 // =====================

 $.fn.scrollspy.noConflict = function () {
  $.fn.scrollspy = old
  return this
 }


 // SCROLLSPY DATA-API
 // ==================

 $(window).on('load.bs.scrollspy.data-api', function () {
  $('[data-spy="scroll"]').each(function () {
   var $spy = $(this)
   Plugin.call($spy, $spy.data())
  })
 })

}(jQuery);




以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。