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其實滾動監聽使用的情況還是很多的，比如導航居于右側，當主題內容滾動某一塊的時候，右側導航對應的要高亮。
實現功能
1、當滾動區域內設置的hashkey距離頂點到有效位置時，就關聯設置其導航上的指定項
2、導航必須是 .nav > li > a 結構，并且a上href或data-target要綁定hashkey
3、菜單上必須有.nav樣式
4、滾動區域的data-target與導航父級Id（一定是父級）要一致。
<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" > <h5 id="one" >ibe</h5><p>One的具體內容<br/>One的具體內容<br/>One的具體內容<br/>One的具體內容<br/>One的具體內容<br/>One的具體內容<br/></p> <h5 id="two" >two</h5><p>One的具體內容<br/>One的具體內容<br/>One的具體內容<br/>One的具體內容<br/>One的具體內容<br/>One的具體內容<br/></p> <h5 id="three" >three</h5><p>One的具體內容<br/>One的具體內容<br/>One的具體內容<br/>One的具體內容<br/>One的具體內容<br/>One的具體內容<br/></p> </div>
下面來看一下實現的具體代碼，原理：當滾動容器內的hashkey位置距離容器頂部只有 offset設置的值，就會設置導航中對應的href高亮。
ScrollSpy構造函數
首先新建一個構造函數，如下：
function ScrollSpy(element, options) {
this.$body = $(document.body)
this.$scrollElement = $(element).is(document.body) ? $(window) : $(element)
this.options = $.extend({}, ScrollSpy.DEFAULTS, options)
this.selector = (this.options.target || '') + ' .nav li > a'
this.offsets = []
this.targets = []
this.activeTarget = null
this.scrollHeight = 0
this.$scrollElement.on('scroll.bs.scrollspy', $.proxy(this.process, this))
this.refresh()
this.process()
}
該構造函數主要干了啥：
1.基本設置，主要是設置當前滾動元素是設置的body還是具體的某一塊元素；其次是導航的結構要是.nav li > a的結構，也就是你的菜單中也要有.nav這個class。
2.監聽元素滾動的時候，執行process方法。
3.同時初始化的時候也執行了refresh與process方法。
下面講解一下這幾個方法。
getScrolHeight方法
獲取滾動容器的內容高度（包含被隱藏部分）
this.$scrollElement[0].scrollHeight || Math.max(this.$body[0].scrollHeight, document.documentElement.scrollHeight)
refresh方法
刷新并存儲滾動容器內各hashkey的值
ScrollSpy.prototype.refresh = function () {
var that = this
var offsetMethod = 'offset'
var offsetBase = 0
this.offsets = []
this.targets = []
this.scrollHeight = this.getScrollHeight()
if (!$.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])
})
}
它主要實現了什么呢？
1.默認用offset來獲取定位值，如果滾動區域不是window則用position來獲取
if (!$.isWindow(this.$scrollElement[0])) {
offsetMethod = 'position'
offsetBase = this.$scrollElement.scrollTop()
}
2.根據導航上的hashkey來遍歷獲取 滾動區域內的hashkey對應的offset值：
this.$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
滾動條事件觸發函數，用于計算當前需要高亮那個導航菜單
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.獲取滾動容器已滾動距離：
var scrollTop = this.$scrollElement.scrollTop() + this.options.offset
2.滾動容器可以滾動的最大高度:
var maxScroll = this.options.offset + scrollHeight - this.$scrollElement.height()
3.設置滾動元素邏輯，給當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
設置指定的導航菜單高亮
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
清除所有高亮菜單
ScrollSpy.prototype.clear = function () {
$(this.selector)
.parentsUntil(this.options.target, '.active')
.removeClass('active')
}
源碼
+function ($) {
'use strict';
// SCROLLSPY CLASS DEFINITION
// ==========================
function ScrollSpy(element, options) {
this.$body = $(document.body)
this.$scrollElement = $(element).is(document.body) ? $(window) : $(element)
this.options = $.extend({}, ScrollSpy.DEFAULTS, options)
this.selector = (this.options.target || '') + ' .nav li > a'
this.offsets = []
this.targets = []
this.activeTarget = null
this.scrollHeight = 0
this.$scrollElement.on('scroll.bs.scrollspy', $.proxy(this.process, this))
this.refresh()
this.process()
}
ScrollSpy.VERSION = '3.3.7'
ScrollSpy.DEFAULTS = {
offset: 10
}
ScrollSpy.prototype.getScrollHeight = function () {
return this.$scrollElement[0].scrollHeight || Math.max(this.$body[0].scrollHeight, document.documentElement.scrollHeight)
}
ScrollSpy.prototype.refresh = function () {
var that = this
var offsetMethod = 'offset'
var offsetBase = 0
this.offsets = []
this.targets = []
this.scrollHeight = this.getScrollHeight()
if (!$.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])
})
}
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])
}
}
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')
}
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內容，希望對大家的學習有所幫助，也希望大家多多支持億速云。
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