Scroll a message across the browser tab's Title and/or URL hash

scrollMessage.js

function scrollMessage(message, timeoutMs, changeTitle, changeUrl) {
  if (!message || !(changeTitle || changeUrl)) return function stopScroll() {}

  if (changeTitle) document.title = message
  if (changeUrl) document.location.hash = message
  
  function init() {
    var index = 0
    function scrollerTick() {
      index = (index + 1) % message.length
      var scrolledMessage = message.substr(index) + message.substring(0, index)
      if (changeTitle) document.title = scrolledMessage
      if (changeUrl) document.location.hash = scrolledMessage
    }
    return setInterval(scrollerTick, Number(timeoutMs) || 500)
  }

  var clearId = init()
  return function stopScroll() { clearInterval(clearId) }
}