scrollspy.js

/* =============================================================
 * Bootstrap: scrollspy.js v3.0.0
 * http://twitter.github.com/bootstrap/javascript.html#scrollspy
 * =============================================================
 * Copyright 2012 Twitter, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * ============================================================== */


!function ($) { "use strict";

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

  function ScrollSpy(element, options) {
    var href
    var process  = $.proxy(this.process, this)
    var $element = $(element).is('body') ? $(window) : $(element)

    this.$body          = $('body')
    this.$scrollElement = $element.on('scroll.scroll-spy.data-api', process)
    this.options        = $.extend({}, ScrollSpy.DEFAULTS, options)
    this.selector       = (this.options.target
      || ((href = $(element).attr('href')) && href.replace(/.*(?=#[^\s]+$)/, '')) //strip for ie7
      || '') + ' .nav li > a'
    this.offsets        = $([])
    this.targets        = $([])
    this.activeTarget   = null

    this.refresh()
    this.process()
  }

  ScrollSpy.DEFAULTS = {
    offset: 10
  }

  ScrollSpy.prototype.refresh = function () {
    this.offsets = $([])
    this.targets = $([])

    var self     = this
    var $targets = this.$body
      .find(this.selector)
      .map(function () {
        var $el   = $(this)
        var href  = $el.data('target') || $el.attr('href')
        var $href = /^#\w/.test(href) && $(href)

        return ($href
          && $href.length
          && [[ $href.position().top + (!$.isWindow(self.$scrollElement.get(0)) && self.$scrollElement.scrollTop()), href ]]) || null
      })
      .sort(function (a, b) { return a[0] - b[0] })
      .each(function () {
        self.offsets.push(this[0])
        self.targets.push(this[1])
      })
  }

  ScrollSpy.prototype.process = function () {
    var scrollTop    = this.$scrollElement.scrollTop() + this.options.offset
    var scrollHeight = this.$scrollElement[0].scrollHeight || this.$body[0].scrollHeight
    var maxScroll    = scrollHeight - this.$scrollElement.height()
    var offsets      = this.offsets
    var targets      = this.targets
    var activeTarget = this.activeTarget
    var i

    if (scrollTop >= maxScroll) {
      return activeTarget != (i = targets.last()[0]) && this.activate(i)
    }

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

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

    $(this.selector)
      .parents('.active')
      .removeClass('active')

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

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

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

    active.trigger('activate')
  }


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

  var old = $.fn.scrollspy

  $.fn.scrollspy = function (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]()
    })
  }

  $.fn.scrollspy.Constructor = ScrollSpy


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

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


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

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

}(window.jQuery);