Idle timer

idle_timer.js

function createIdleTimer (delay = 5E3) {
    const IDLE_POLL_TIMEOUT = 1E2

    const events = ['mousemove', 'mousedown', 'keydown', 'touchstart', 'scroll']

    return new Promise((resolve) => {
        let idle = true
        let timeout = null
        let lastTimestamp = null
        let elapsedTimeInMillis = 0

        function registerEvents () {
            events.forEach((event) => window.addEventListener(event, handleEvent))
        }

        function unregisterEvents () {
            events.forEach((event) => window.removeEventListener(event, handleEvent))
        }

        function signalTimer () {
            unregisterEvents()
            resolve()
        }

        function handleEvent () {
            if (elapsedTimeInMillis > delay) {
                signalTimer()
                return
            }

            if (idle) {
                idle = false
                lastTimestamp = Date.now()
            }

            clearTimeout(timeout)

            timeout = setTimeout(() => {
                idle = true
                elapsedTimeInMillis += Date.now() - lastTimestamp

                if (elapsedTimeInMillis > delay) {
                    signalTimer()
                }
            }, IDLE_POLL_TIMEOUT)
        }

        registerEvents()
    })
}

createIdleTimer().then(() => console.log('5 seconds of activity!'))