Is Element Visible In Viewport

$.fn.isOnScreen = function () {
  var win = $(window)

  var viewport = {
    top: win.scrollTop(),
    left: win.scrollLeft(),
  }
  viewport.right = viewport.left + win.width()
  viewport.bottom = viewport.top + win.height()

  var bounds = this.offset()
  bounds.right = bounds.left + this.outerWidth()
  bounds.bottom = bounds.top + this.outerHeight()

  return !(
    viewport.right < bounds.left ||
    viewport.left > bounds.right ||
    viewport.bottom < bounds.top ||
    viewport.top > bounds.bottom
  )
}