mail_script.html

<script>
function sendEmail(){
    var subject = document.getElementById('subject');
    var body = document.getElementById('message');
    
    var startRow = document.getElementById('startRow');
    var emailColumn = document.getElementById('emailColumn');
    var members = document.getElementById('members');
        
    if (subject.value == "") {
        setError(subject, "Detta fält får ej vara tomt!");
    } else if (body.value == "") {
        setError(body, "Detta fält får ej vara tomt!");
    } else {
        var dataNlToBr = body.value.replace(/\r?\n/g, '<br>');
        
        if (!$.isNumeric(startRow.value) && startRow.value != "") {
            setError(startRow, "Endast numeriskt!");
        } else if (!$.isNumeric(emailColumn.value) && emailColumn.value != "") {
            setError(emailColumn, "Endast numeriskt!");
        } else if (!$.isNumeric(members.value) && members.value != "") {
            setError(members, "Endast numeriskt!");
        }else {
            google.script.run.sendEmails(subject.value, dataNlToBr, startRow.value, emailColumn.value, members.value, attachments);
        }        
    }
}

function showAdvanced(){
    $( "#advanced" ).slideToggle( "fast", function() {
        var buttons = document.getElementById('bottomButtons');
        buttons.scrollIntoView({behavior: 'smooth' });
    });
    $( "#advancedToggle" ).toggleClass('glyphicon-chevron-up glyphicon-chevron-down');
    window.scrollTo(0,document.body.scrollHeight);
}

function setError(elementTag, message) {
    elementTag.parentElement.classList.add("has-error");
    elementTag.value = "";
    elementTag.placeholder = message
}
</script>