code: function intervalStuff() {
  
      var message = "doing interval stuff at " + new Date()
  
      // add a timeout
      setTimeout(function() { console.log(message)}, 333)
  
      // add a timeline marker
      console.markTimeline(message)
  
      // write to local- and sessionStorage
      if (window.localStorage) {
          var smessage = message + " (local)"
          window.localStorage.setItem(  "item-" + storageIndex, smessage)
      }
  
      if (window.sessionStorage) {
          var smessage = message + " (session)"
          window.sessionStorage.setItem("item-" + storageIndex, smessage)
      }
      storageIndex++
  
      // write the message to the page
      output(message)
  
      // do an XHR
      var xhr = new XMLHttpRequest()
      // xhr.addEventListener("readystatechange", function() {logXhr(this)})
      xhr.open("GET", "../target/target-script.js", true)
      xhr.send()
  }
docs: ------------------------------------------------------------------------------