Using navigator.sendBeacon and Fetch to send analytics data.

Use the page event :

visibilitychange

function checkVisibilityControl() {
if (typeof document.hidden !== “undefined”) {
return {
hidden: “hidden”,
visibilityChange: “visibilitychange”,
}// Opera 12.10 and Firefox 18 and later support
}
if (typeof document.msHidden !== “undefined”) {
return {
hidden: “msHidden”,
visibilityChange: “msvisibilitychange”
}
}
if (typeof document.webkitHidden !== “undefined”) {
return {
hidden: “webkitHidden”,
visibilityChange: “webkitvisibilitychange”
}
}
return {
hidden: ‘’,
visibilityChange: ‘pagehide’
}
}

in order to send the event use the navigator.sendBeacon (doesn’t allows for getting errors), or use the fetch api, which allows for dealing with errors and use the parameter ‘keepalive’ : true, this is to avoid the request to be interrupted in case browser close.