Validation from submitting in Apps Script - google-apps-script

Question

Please I need help. I have the same need of this post. I followed the instructions but I can't find my error. I'm frustratred.
When I submit with null fields, the script shows me a blank page.
When I submit with complete fields, the script shows me a blank page also and never upload the file.
This is my final code:
code.gs
function doGet(e) {
return HtmlService.createHtmlOutputFromFile('form.html');
}
function uploadFiles(form) {
try {
var dropbox = "NHD Papers";
var folder, folders = DriveApp.getFoldersByName(dropbox);
if (folders.hasNext()) {
folder = folders.next();
} else {
folder = DriveApp.createFolder(dropbox);
}
var blob = form.myFile;
var file = folder.createFile(blob);
file.setDescription("Uploaded by " + form.myName + ", Division: " + form.myDivision + ", School: " + form.mySchool + ", State: " + form.myState);
return "<h2>File uploaded successfully!</h2><p>Copy and paste the following URL into registration:<br /><br /><strong>" + file.getUrl() + '</strong></p>';
} catch (error) {
return error.toString();
}
}
form.html
<p>
<form id="myForm" onsubmit="validateForm();">
<h1>NHD Paper Upload</h1>
<label>Name</label>
<input type="text" name="myName" class="required" placeholder="Enter your full name..">
<label>Division</label>
<input type="text" name="myDivision" class="required" placeholder="(ex. Junior or Senior)">
<label>School</label>
<input type="text" name="mySchool" class="required" placeholder="Enter your school..">
<label>Affiliate</label>
<input type="text" name="myAffiliate" class="required" placeholder="Enter your affiliate..">
<label>Select file to upload. </label>
<input type="file" name="myFile">
<input type="submit" value="Submit File" >
<br />
</form>
</p>
<div id="output"></div>
<script>
function validateForm() {
var x=document.getElementsByClassName('required');
for(var i = 0; i <x.length; i++){
if (x[i].value == null || x[i].value == "")
{
alert("All fields must be filled out.");
return false;
}
this.value='Please be patient while your paper is uploading..';
var myFormObject = document.getElementById('myForm');
google.script.run.withSuccessHandler(fileUploaded)
.uploadFiles(myFormObject);
}
}
function fileUploaded(status) {
document.getElementById('myForm').style.display = 'none';
document.getElementById('output').innerHTML = status;
}
</script>
<style>
input { display:block; margin: 15px; }
p {margin-left:20px;}
</style>
Regards,

Answer 1

In the IFRAME mode HTML forms are allowed to submit, but if the form has no action attribute it will submit to a blank page.
The solution suggested by the official documentation is to add the following JavaScript code to prevent all form submitions on load:
<script>
// Prevent forms from submitting.
function preventFormSubmit() {
var forms = document.querySelectorAll('form');
for (var i = 0; i < forms.length; i++) {
forms[i].addEventListener('submit', function(event) {
event.preventDefault();
});
}
}
window.addEventListener('load', preventFormSubmit);
</script>
You can also add a return false; or event.preventDefault() at the end of your validateForm() function.