bootstrap-scrollspy.js

/* =============================================================
 * bootstrap-scrollspy.js v2.0.0
 * 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 ) {
    var process = $.proxy(this.process, this)

    this.$scrollElement = $(element).on('scroll.scroll.data-api', process)
    this.selector = (this.$scrollElement.attr('data-target')
      || this.$scrollElement.attr('href')
      || '') + ' .nav li > a'
    this.$body = $('body').on('click.scroll.data-api', this.selector, process)

    this.refresh()
    this.process()
  }

  ScrollSpy.prototype = {

      constructor: ScrollSpy

    , refresh: function () {
        this.targets = this.$body
          .find(this.selector)
          .map(function () {
            var href = $(this).attr('href')
            return /^#\w/.test(href) && $(href).length ? href : null
          })

        this.offsets = $.map(this.targets, function (id) {
          return $(id).position().top
        })
      }

    , process: function () {
        var scrollTop = this.$scrollElement.scrollTop() + 10
          , offsets = this.offsets
          , targets = this.targets
          , activeTarget = this.activeTarget
          , i

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

    , activate: function (target) {
        var active

        this.activeTarget = target

        this.$body
          .find(this.selector).parent('.active')
          .removeClass('active')

        active = this.$body
          .find(this.selector + '[href="' + target + '"]')
          .parent('li')
          .addClass('active')

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

  }


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

  $.fn.scrollspy = function ( option ) {
    return this.each(function () {
      var $this = $(this)
        , data = $this.data('scrollspy')
      if (!data) $this.data('scrollspy', (data = new ScrollSpy(this)))
      if (typeof option == 'string') data[option]()
    })
  }

  $.fn.scrollspy.Constructor = ScrollSpy


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

  $(function () { $('[data-spy="scroll"]').scrollspy() })

}( window.jQuery )