Get an array representing the hours a person is active on Whatsapp. Saved to local Storage and viewable by using 'console.log(hoursArray)'

WhatsappStalker.js

var LOCAL_STORAGE_KEY = "activelogintimestatistics"
var lastSeenTime
var localStorageData = localStorage[LOCAL_STORAGE_KEY]
var localStorageArray = localStorageData != undefined ? JSON.parse(localStorageData) : undefined
var hoursArray = (localStorageArray == undefined) ? [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] : localStorageArray
console.log(hoursArray)
update = function() {
    var textSpan = document.getElementsByClassName("emojitext O90ur")[0]
    if (textSpan == null) {
        console.log("An error has occured, couldn't find the last seen label")
        return
    }
    var text = textSpan.innerText
    if (text == "online") {
        var currentTime = new Date()
        var currentHour = currentTime.getHours()
        addMinute(parseInt(hour))
        console.log("Adding to " + currentHour + " Because User is online")
        return
    }
    text = text.substr(10, text.length)
    var day = text.substr(0, text.indexOf(" at"))
    if (day == "today") {
        var newestLastSeen = text.substr(text.indexOf(" at") + 3, text.length)
        console.log(newestLastSeen)
        if (newestLastSeen != lastSeenTime) {
            var hour = newestLastSeen.substr(0, newestLastSeen.indexOf(":"))
            console.log("adding to" + hour)
            lastSeenTime = newestLastSeen
            addMinute(parseInt(hour))
            console.log("Minutes logged in on that hour: " + hoursArray[parseInt(hour)])
        } else {
            console.log("Not adding because user didn't login since last login")
            return
        }
    } else {
        console.log("Not adding because user didn't login today yet")
        return
    }
}

function addMinute(index) {
    hoursArray[index] = hoursArray[index] + 1
    localStorage[LOCAL_STORAGE_KEY] = JSON.stringify(hoursArray);
}

setInterval(update, 60000)