confirmation_mail_script.html

<script>
$(function() {setDefaultValues();});

function setDefaultValues() {     
  google.script.run
      .withFailureHandler(function(err){
          console.error("error occured", e);
      })
      .withSuccessHandler(function(res){
           $( "#recipient" ).val(res);
      })
      .getBottomMemberEmail();
      
  google.script.run
      .withFailureHandler(function(err){
          console.error("error occured", e);
      })
      .withSuccessHandler(function(res){
           $( "#subject" ).val(res);
      })
      .getWelcomeMessageSubject();
      
  google.script.run
      .withFailureHandler(function(err){
          console.error("error occured", e);
      })
      .withSuccessHandler(function(res){
           $( "#message" ).val(res);
      })
      .getWelcomeMessage(); 
}

function sendRegistrationConfirmationMail(){
    
    var recipient = document.getElementById("recipient");
    var subject = document.getElementById('subject');
    var body = document.getElementById('message');
        
    if (subject.value == "") {
        setError(subject, "Detta fält får ej vara tomt!");
    } else if (body.value == "") {
        setError(body, "Detta fält får ej vara tomt!");
    } else if (recipient.value == "") {
        setError(recipient, "Detta fält får ej vara tomt!");
    } else {
        var dataNlToBr = body.value.replace(/\r?\n/g, '<br>'); 
        google.script.run.sendRegistrationConfirmationMail(recipient.value, subject.value, dataNlToBr, attachments);
    }
}
</script>