List all Labels of an email to Spreadsheet - email

Question

My emails usually has more than one Labels assigned. I like to search emails with a specific label then list them into the spreadsheet and show all other labels also assigned to the email.
Here's what i have so far, can't figure out how to get the other labels...
function myFunction() {
var ss = SpreadsheetApp.getActiveSheet();
var threads = GmailApp.search("label:Test");
for (var i=0; i<threads.length; i++)
{
var messages = threads[i].getMessages();
for (var j=0; j<messages.length; j++)
{
var sub = messages[j].getSubject();
var from = messages[j].getFrom();
var dat = messages[j].getDate();
ss.appendRow([dat, sub, from])
}
}
}

Answer 1

As far as Apps Script is concerned, Gmail labels are applied to threads and not to individual messages. (There are other contexts where this isn't necessarily true, as a Web Apps post details).
So, you should use the getLabels method of the Thread object. It then makes sense to structure the output so that each row corresponds to a thread, rather than a message. This is what I did below. The script takes subject/from/date from the first message in each thread. The 4th column is the comma-separated list of labels, except the one you search for.
function myFunction() {
var sheet = SpreadsheetApp.getActiveSheet();
var search_label = 'Test';
var threads = GmailApp.search('label:' + search_label);
var output = [];
for (var i=0; i < threads.length; i++) {
var firstMessage = threads[i].getMessages()[0];
var sub = firstMessage.getSubject();
var from = firstMessage.getFrom();
var dat = firstMessage.getDate();
var labels = threads[i].getLabels();
var otherLabels = [];
for (var j = 0; j < labels.length; j++) {
var labelName = labels[j].getName();
if (labelName != search_label) {
otherLabels.push(labelName);
}
}
output.push([dat, sub, from, otherLabels.join(', ')]);
}
sheet.getRange(1, 1, output.length, output[0].length).setValues(output);
}
I prefer not to add one row at a time, instead gathering the double array output and inserting it all at once. Of course you can use appendRow as in your script. Then you wouldn't necessarily need a comma-separated list,
sheet.appendRow([dat, sub, from].concat(otherLabels));
would work.