Hidden counter

gistfile1.coffee

# Adapted slightly from Sam Dutton
  # Set name of hidden property and visibility change event
  # since some browsers only offer vendor-prefixed support
  hidden = undefined
  state = undefined
  visibilityChange = undefined
  if typeof document.hidden isnt "undefined"
    hidden = "hidden"
    visibilityChange = "visibilitychange"
    state = "visibilityState"
  else if typeof document.mozHidden isnt "undefined"
    hidden = "mozHidden"
    visibilityChange = "mozvisibilitychange"
    state = "mozVisibilityState"
  else if typeof document.msHidden isnt "undefined"
    hidden = "msHidden"
    visibilityChange = "msvisibilitychange"
    state = "msVisibilityState"
  else if typeof document.webkitHidden isnt "undefined"
    hidden = "webkitHidden"
    visibilityChange = "webkitvisibilitychange"
    state = "webkitVisibilityState"

  setHiddenCounter = (start_hidden_time) ->
    time = new Date().getTime()
    timestamp = (time - start_hidden_time) / 1000

    if $(".hidden_timestamp").val() != ""
      $(".hidden_timestamp").val(parseInt($(".hidden_timestamp").val()) + timestamp)
    else
      $(".hidden_timestamp").val(timestamp)

  # Add a listener that constantly changes the title
  hiddent_counter_interval_id = undefined
  document.addEventListener visibilityChange, (->
    if document[state] == "hidden"
      hiddent_counter_interval_id = new Date().getTime()
    else
      setHiddenCounter(hiddent_counter_interval_id)
      hiddent_counter_interval_id = undefined
  ), false