A simple way to track how far users are scrolling. Assumes you are using Mixpanel and jQuery. Copyright © 2013 David Strauß MIT License

example.js

new MixpanelScrollTracker({
  attribute: 'section',
  event: 'Scrolled to',
  markers: [
    { position: 500, value: 'Services' },
    { position: 700, value: 'About Us' },
    { position: 900, value: 'Contact Form' }
  ]
});

mixpanel_scroll_tracker.coffee

class MixpanelScrollTracker
  constructor: (options) ->
    @markers = options.markers.sort @compareMarkers
    @event = options.event
    @attribute = options.attribute
    @intervalID = setInterval @tick, 500

  tick: =>
    currentPosition = $(window).scrollTop()

    while @markers.length > 0 && currentPosition >= @markers[0].position
      mixpanelObject = {}
      mixpanelObject[@attribute] = @markers[0].value

      mixpanel.track @event, mixpanelObject

      @markers.shift()

    @stopTracking() if @lastMarkerIsReached()

  compareMarkers: (a, b) -> a.position >= b.position ? -1 : 1

  lastMarkerIsReached: -> @markers.length == 0

  stopTracking: -> clearInterval @intervalID

window.MixpanelScrollTracker = MixpanelScrollTracker

mixpanel_scroll_tracker.min.js

(function(){var t,r=function(t,r){return function(){return t.apply(r,arguments)}};t=function(){function t(t){this.tick=r(this.tick,this),this.markers=t.markers.sort(this.compareMarkers),this.event=t.event,this.attribute=t.attribute,this.intervalID=setInterval(this.tick,500)}return t.prototype.tick=function(){var t,r;for(t=$(window).scrollTop();this.markers.length>0&&t>=this.markers[0].position;)r={},r[this.attribute]=this.markers[0].value,mixpanel.track(this.event,r),this.markers.shift();return this.lastMarkerIsReached()?this.stopTracking():void 0},t.prototype.compareMarkers=function(t,r){var i;return null!=(i=t.position>=r.position)?i:-{1:1}},t.prototype.lastMarkerIsReached=function(){return 0===this.markers.length},t.prototype.stopTracking=function(){return clearInterval(this.intervalID)},t}(),window.MixpanelScrollTracker=t}).call(this);