Add multiple dynamic attachments to email - google-apps-script

Question

I'm listing all PDF files of a folder and send them into an email.
The issue is that I don't know how attach multiple files.
This is what I've tried so far: put files into blob then pass it.
Other try was to put blob[0] and blob1 if there is 2 pdf files but it doesn't work.
var folders = DriveApp.getFoldersByName(folderToScan);
var folder = folders.next();
var contents = folder.getFiles();
var blob = [];
var filesTextList = "";
// foreach file
for(var counter = 0;contents.hasNext();counter++)
{
file = contents.next();
var MimeType = file.getMimeType();
// filter PDF
if(file.getMimeType() == "application/pdf")
{
blob[counter] = file.getBlob();
// add file name to text
filesTextList += "\n" + file.getName();
}
}
MailApp.sendEmail(sender, subject, message,
{attachments: blob}
);
If I only have 1 blob file, {attachments: blob[0]} is working but it's not dynamic
Here is the debugger at the line of the mail:

Answer 1

The attachments parameter of sendEmail method takes "an array of files to send with the email". They can be File objects, you don't have to get blobs from them.
More importantly, your loop will create an array with undefined elements because blob[counter] only gets assigned when the file is a PDF, but the value of counter increases regardless. I don't think sendEmail will be happy about that.
Use while loop with iterators, and push method to add elements to an array. A complete example.
function emailatt() {
var contents = DriveApp.getFolderById("id here").getFiles();
var attachments = [];
while (contents.hasNext()) {
var file = contents.next();
if (file.getMimeType() == "application/pdf") {
attachments.push(file);
}
}
MailApp.sendEmail("user#example.com", "subject", "body", {attachments: attachments});
}
Aside: getting folder by Id is best when you know what folder you want. Using getFoldersByName and then picking whatever folder with that name came up first is a less robust approach.