progress-indicator.js

var $win = $(window)
var $progress = $('.progress-indicator')
var wh = $win.height()
var h = $('body').height()
var scrollHeight = h - wh

$win.on('scroll', function () {
  var perc = Math.max(0, Math.min(1, $win.scrollTop() / scrollHeight))

  $progress.css({
    width: perc * 100 + '%'
  })
})