JavaScript Reminder

function reminder() {
    if (!confirm('Do you want to set a reminder?'))
        return;
    var reason = prompt('What do you want to be reminded?');
    if (reason == null)
        return;
    var hr = prompt('How many hours from now do you want to be reminded?\n\n(Whole numbers only)');
    if (hr == null)
        return;
    if (!Number.isInteger(Number(hr))) {
        alert('Invalid Input!\nPlease type a number!');
        return;
    }
    var min = prompt('How many minutes from now do you want to be reminded?\n\n(Whole numbers only)');
    if (min == null)
        return;
    if (!Number.isInteger(Number(min))) {
        alert('Invalid Input!\nPlease type a number!');
        return;
    }
    var sec = prompt('How many seconds from now do you want to be reminded?\n\n(Whole numbers only)');
    if (sec == null)
        return;
    if (!Number.isInteger(Number(sec))) {
        alert('Invalid Input!\nPlease type a number!');
        return;
    }
    hr *= 60
    hr *= 60
    hr *= 1000
    min *= 60
    min *= 1000
    sec *= 1000
    setTimeout(function() {
        alert('Reminder:\n' + reason);
    }, hr + min + sec);
    alert('Your reminder has been set!');
}
reminder();