node.js event based game loop

index.js

const bigInt = require('big-integer')

function getCurrentMonoTime () {
  const [s, n] = process.hrtime()
  return bigInt(s).times(1000000000).plus(n)
}

const bootGameTime = 0
const bootMonoTime = getCurrentMonoTime()

function getCurrentGameTime () {
  const msSinceBoot = getCurrentMonoTime().minus(bootMonoTime).divide(1000000).toJSNumber()
  return bootGameTime + msSinceBoot
}

let watchdog = null
let events = []

function spawnWatchdog (targetTime) {
  let now = getCurrentGameTime()

  watchdog = setTimeout(function () {
    watchdogCb(targetTime)
  }, targetTime - now)
}

function killWatchdog () {
  clearTimeout(watchdog)
}

function refreshWatchdog () {
  if (events.length > 0) {
    const minT = Math.min(...events.map(e => e.t))
    spawnWatchdog(minT)
  }
}

function watchdogCb (t) {
  const currentGameTime = getCurrentGameTime()

  console.log(`woke up! currentGameTime: ${currentGameTime}`)

  events = events.filter(e => {
    if (currentGameTime >= e.t) {
      // run it and remove it
      e.fn(currentGameTime)
      return false
    } else {
      // keep it
      return true
    }
  })

  refreshWatchdog()
}

function schedule (fn, t) {
  killWatchdog()
  events.push({ fn, t })
  refreshWatchdog()
}

// test it

schedule(function (t) {
  console.log(`I was scheduled for t = 0 and it is currently ${t}`)
}, 0)

schedule(function (t) {
  console.log(`I was scheduled for t = 0 and it is currently ${t}`)
}, 0)

schedule(function (t) {
  console.log(`I was scheduled for t = 0 and it is currently ${t}`)
}, 0)

schedule(function (t) {
  console.log(`I was scheduled for t = 0 and it is currently ${t}`)
}, 0)

schedule(function (t) {
  console.log(`I was scheduled for t = 1000 and it is currently ${t}`)
}, 1000)

schedule(function (t) {
  console.log(`I was scheduled for t = 1010 and it is currently ${t}`)
}, 1010)

schedule(function (t) {
  console.log(`I was scheduled for t = 1020 and it is currently ${t}`)
}, 1020)

schedule(function (t) {
  console.log(`I was scheduled for t = 1030 and it is currently ${t}`)
}, 1030)

schedule(function (t) {
  console.log(`I was scheduled for t = 2000 and it is currently ${t}`)
}, 2000)

schedule(function (t) {
  console.log(`I was scheduled for t = 3000 and it is currently ${t}`)
}, 3000)

schedule(function (t) {
  console.log(`I was scheduled for t = 10000 and it is currently ${t}`)
}, 10000)