Bootstrap滾動(dòng)監(jiān)聽組件scrollspy.js使用方法詳解

其實(shí)滾動(dòng)監(jiān)聽使用的情況還是很多的，比如導(dǎo)航居于右側(cè)，當(dāng)主題內(nèi)容滾動(dòng)某一塊的時(shí)候，右側(cè)導(dǎo)航對(duì)應(yīng)的要高亮。

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實(shí)現(xiàn)功能

1、當(dāng)滾動(dòng)區(qū)域內(nèi)設(shè)置的hashkey距離頂點(diǎn)到有效位置時(shí)，就關(guān)聯(lián)設(shè)置其導(dǎo)航上的指定項(xiàng)
2、導(dǎo)航必須是 .nav > li > a 結(jié)構(gòu)，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(dòng)區(qū)域的data-target與導(dǎo)航父級(jí)Id（一定是父級(jí)）要一致。

 
 
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下面來看一下實(shí)現(xiàn)的具體代碼，原理：當(dāng)滾動(dòng)容器內(nèi)的hashkey位置距離容器頂部只有 offset設(shè)置的值，就會(huì)設(shè)置導(dǎo)航中對(duì)應(yīng)的href高亮。

ScrollSpy構(gòu)造函數(shù)

首先新建一個(gè)構(gòu)造函數(shù)，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(gòu)造函數(shù)主要干了啥：

1.基本設(shè)置，主要是設(shè)置當(dāng)前滾動(dòng)元素是設(shè)置的body還是具體的某一塊元素；其次是導(dǎo)航的結(jié)構(gòu)要是.nav li > a的結(jié)構(gòu)，也就是你的菜單中也要有.nav這個(gè)class。

2.監(jiān)聽元素滾動(dòng)的時(shí)候，執(zhí)行process方法。

3.同時(shí)初始化的時(shí)候也執(zhí)行了refresh與process方法。

下面講解一下這幾個(gè)方法。

getScrolHeight方法

獲取滾動(dòng)容器的內(nèi)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(chǔ)滾動(dòng)容器內(nèi)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(shí)現(xiàn)了什么呢？

1.默認(rèn)用offset來獲取定位值，如果滾動(dòng)區(qū)域不是window則用position來獲取

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

2.根據(jù)導(dǎo)航上的hashkey來遍歷獲取滾動(dòng)區(qū)域內(nèi)的hashkey對(duì)應(yīng)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(dòng)條事件觸發(fā)函數(shù)，用于計(jì)算當(dāng)前需要高亮那個(gè)導(dǎo)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(dòng)容器已滾動(dòng)距離：

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

2.滾動(dòng)容器可以滾動(dòng)的最大高度:

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

3.設(shè)置滾動(dòng)元素邏輯，給當(dāng)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(shè)置指定的導(dǎo)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(nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持創(chuàng)新互聯(lián)。

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