function isIOS() {
    let tester = new RegExp("/iPad|iPhone|iPod/")
    let IOSdetected = tester.test(navigator.userAgent)
    let msStreamNotUsed = isNullOrUndefined(window.MSStream) //prevent fake user agent in internet explorer

    if (IOSdetected === true && msStreamNotUsed) {
        return true
    }
    return false
}

function isNullOrUndefined(input) {
    return input === null || input === undefined
}