x.js

var isset = false
var interval
var assert = require('assert')
var doNT = !!process.argv[2]

function set() {
  console.error(arguments.callee.name)
  assert(!isset)
  isset = true
  interval = setInterval(intFn)
}

function clear() {
  console.error(arguments.callee.name)
  assert(isset)
  isset = false
  if (doNT)
    process.nextTick(clear_)
  else
    clear_()
}

function clear_() {
  console.error(arguments.callee.name)
  clearInterval(interval)
}

function intFn() {
  console.error(arguments.callee.name)
  assert(isset)
  timeouts()
}

function timeouts() {
  console.error(arguments.callee.name)
  setTimeout(toFn)
  setTimeout(toFn)
  setTimeout(toFn)
}

function toFn() {
  console.error(arguments.callee.name)
  if (!isset)
    set()
  else
    clear()
}

toFn()

/*
$ ./node x.js
toFn
set
intFn
timeouts
toFn
clear
clear_
toFn
set
toFn
clear
clear_

$ ./node x.js helloyesthisisnexttick
toFn
set
intFn
timeouts
toFn
clear
toFn
set
toFn
clear
intFn

assert.js:98
  throw new assert.AssertionError({
        ^
AssertionError: false == true
    at intFn (/Users/isaacs/dev/js/node-master/x.js:30:3)
    at wrapper [as _onTimeout] (timers.js:249:14)
    at Timer.listOnTimeout (timers.js:107:15)
*/