Download a PDF generated by Apps Script via web app - pdf

Question

I'm trying to figure out how to make a Google Apps Script deployed as a web app download a PDF that's generated on a click. It almost works, but the resulting file isn't valid. I can't figure out if it's an encoding issue or something else.
In Apps Script the code looks simple:
function makePDF() {
...
var pdfBlob = doc.getAs('application/pdf');
return Utilities.base64Encode(pdfBlob.getBytes());
}
In the browser, there's a click handler:
function clickHandler(ev) {
ev.preventDefault();
google.script.run
.withSuccessHandler(function(data) {
var pdf = new Blob([window.atob(data)]);
var href = window.URL.createObjectURL(pdf);
var link = document.querySelector('#hiddenLink');
link.href = href;
link.click();
})
.makePDF();
}
Any suggestions?
Thanks!

Answer 1

I figured it out, so posting the answer if anyone else is trying to pass a PDF from Apps Script to the client javascript. It's all much simpler than I had made it.
Rather than messing around with base64 encodings, just pass back the bytes array:
function makePDF() {
...
var pdfBlob = DocumentApp.openById('1234').getAs('application/pdf');
return pdfBlob.getBytes();
}
Now, on the client side, construct a new Blob from an ArrayBuffer. That's easy too:
function clickHandler(ev) {
google.script.run
.withSuccessHandler(function(data) {
var arr = new Uint8Array(data);
var blob = new Blob([arr.buffer], {type: 'application/pdf'});
var obj_url = window.URL.createObjectURL(blob);
var hiddenLink = document.getElementById('hiddenPDFLink');
hiddenLink.setAttribute('href', obj_url);
hiddenLink.setAttribute('download', 'filename.pdf');
hiddenLink.click();
})
.makePDF();
}
And that's it! Hope someone else finds this helpful.

Answer 2

I assume that your makePDF function is doing some other stuffs/Calculation and at the end you need that document to be downloaded to local computer.
What you can do is inside success handler
var link = document.querySelector('#hiddenLink');
link.href = "https://docs.google.com/feeds/download/documents/export/Export?id=**TheIdOfDocumenToBeDownloaded**&exportFormat=pdf";
link.click();
It will then give you a prompt to save document on to local computer.