check viewport if has an element.coffee

  @checkScreenFor: (el) ->
    view =
      top: window.scrollY
      left: window.scrollX
      right: window.scrollX + document.documentElement.clientWidth
      bottom: window.scrollY + document.documentElement.clientHeight

    bounds = el.getBoundingClientRect()
    bounds =
      top: bounds.top + document.body.scrollTop
      left: bounds.left + document.body.scrollLeft
      right: bounds.left + el.offsetWidth
      bottom: bounds.top + el.outerHeight
    !(view.right < bounds.left or view.left > bounds.right or view.bottom < bounds.top or view.top > bounds.bottom)