Simple session tracking using cookies only

session.js

window.addEventListener('load', function() {
    function registerPageView(currentSessionCookieTimestamp) {
        const currentTimestamp = new Date().getTime()
        const fiveMinutes = 5 * 60 * 1000

        if (!currentSessionCookieTimestamp) {
            // ...PV logic...
        } else {
            if (currentTimestamp - currentSessionCookieTimestamp > fiveMinutes) {
                // ...PV logic...
            }
        }        
    }

    function getCookie() {
        // the value being returned is the timestamp of when it was set
        // stored as 'value' in setCookie() below
        const name = 'COOKIE'
        const value = '; ' + document.cookie
        const parts = value.split('; ' + name + '=')

        if (parts.length == 2) {
            return parts
                .pop()
                .split(';')
                .shift()
        }
    }

    function setCookie() {
        const name = 'COOKIE'
        const value = new Date().getTime()
        const date = new Date()

        // Set it expire in 7 days
        date.setTime(date.getTime() + 7 * 24 * 60 * 60 * 1000)

        document.cookie = name + '=' + value + '; expires=' + date.toUTCString() + '; path=/'
    }
    
    const currentSessionCookieTimestamp = getCookie()
    const referrer = !!document.referrer ? document.referrer.split('/')[2] : ''
    const { hostname } = location

    // document.referrer approach ---------------------- 

    if (referrer != hostname) registerPageView(currentSessionCookieTimestamp) 
    window.addEventListener('locationchange', () => setCookie())

    // setInterval approach ---------------------------

    registerPageView(currentSessionCookieTimestamp) 
    setInterval(() => setCookie(), 60000)

    // Always set this on the first load no matter which approach
    setCookie()
})