a basic scroll position detector

gistfile1.txt

class ScrollTracker
  constructor: ->
    $(window).scroll @scroll
    @targets = $ '.targets'
    @sensitivity = 20

  showNavFor: (target)=>
    name = $(target).attr 'name'
    $('.active').removeClass 'active'
    $("a[href=##{name}]").addClass('active');
  
  near: (target)=>
    window.scrollY - @sensitivity < target.offset().top < window.scrollY + @sensitivity

  scroll: (event)=>
    for target in @targets
      @showNavFor target if @near target