Scrolling speed effect

main.js

var last = 0
var offsets = []
$('#content').css('transition', 'all .1s')
$(window).scroll(function(){
  offsets.push(Math.abs(window.scrollY - last))
  last = window.scrollY
})

setInterval(function() {
  var total = 0
  for (var i = 0, len = offsets.length; i < len; i++) {
    total += offsets[i]
  }
  console.log(total)
  offsets = []
  $('#content').width(980 / (1 + total / 500))
}, 100)