function refactoring

previewImage = () ->
  $(".tab-pane").on("mouseenter", "img", (event) ->
    $(event.target).on("mousemove", (move_event) ->
      preview = $(move_event.target).parents(".image_container").find(".preview")
      preview.removeClass("hide").fadeIn(200).addClass("show")
      winH = parseInt($(window).height())
      triangleY = (move_event.screenY / winH) * 316
      triangleY = 0 if triangleY < 0
      $(".triangle").css("top", "#{triangleY}px")
      triangleT = parseInt($(preview).find(".triangle").css("top"))
      winW = parseInt($(window).width()) / 2
      winH = parseInt($(window).height()) / 2
      if move_event.screenX > winW + 167/2
        preview.css("left", "#{(move_event.pageX) - preview.width() - 70}px")
        $(".triangle").removeClass("left").addClass("right")
      else
        preview.css("left", "#{(move_event.pageX) + 40}px")
        $(".triangle").removeClass("right").addClass("left")
      preview.css("top", "#{(move_event.pageY) - triangleT - 20}px")
    )
  )
  $(".tab-pane").on("mouseleave", "img", (event) ->
    $(event.target).off("mousemove")
    $(".preview").removeClass("show").addClass("hide").hide()
    $(".preview").hide()
  )