lifedraft

jQuery.request_scroll = (callback) ->
  
  ###
  Callback for our scroll event - just
  keeps a track on the last scroll value
  ###
  onScroll = ->
    lastScrollY = window.scrollY
    requestTick()

paulirish

What forces layout / reflow

All of the below properties or methods, when requested/called in JavaScript, will trigger the browser to synchronously calculate the style and layout*. This is also called reflow or layout thrashing, and is common performance bottleneck.

Generally, all APIs that synchronously provide layout metrics will trigger forced reflow / layout. Read on for additional cases and details.

Element APIs

Getting box metrics

• elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent