Google Apps Script for loop not processessing all items from getThreads() - google-apps-script

Question

I am attempting to create a function that reads the body of emails and extracts parts to place in a sheet.
I am currently using the below code to pull the emails.
var label = GmailApp.getUserLabelByName("VOIDS");
var threads = label.getThreads();
for (var i = 0; i <= threads.length; i++)
{
var message = threads[i].getMessages();
var body = message[0].getPlainBody();
//email processing//
threads[i].removeLable(label)
}
I've got the loop to do what I need it to do as far as processing the email and placing it where I need it, however it seems to be skipping emails. I've left out the code for the process as it's just a bunch of split() functions on the body variable to extract the appropriate information and paste it into a sheet.
The total number of emails skipped varies based on how many it has to process, but re-running the script results in the same emails being skipped each time.
All emails are having their label removed and all emails are identical save for a few value changes.
This is my first time working with GmailApp outside of sending emails. I'm sure that this is something super simple that I'm just missing, but despite all my Google searching I can't seem to find a solution.
Thank you!

Answer 1

Please bear in mind that getThreads might not return all the threads in your mailbox.
From the official reference docs
getThreads()
Gets the threads that are marked with this label.
This calls fail when the size of all threads is too large for the system to handle. Where the thread size is unknown, and potentially very large, please use getThreads(start, max) and specify ranges of the threads to retrieve in each call.
Resources
https://developers.google.com/apps-script/reference/gmail/gmail-label#getthreads
Related
Trying to understand getThreads in GAS
Make getThreads() app script call count over 500

Answer 2

A thread can contain more than one email
The line var body = message[0].getPlainBody(); implies that you are only proceeding the body of the first message of each thread.
To apply your request t all emails, you need to create a second loop, iterating through each email of each thread.
Sample:
var label = GmailApp.getUserLabelByName("VOIDS");
var threads = label.getThreads();
for (var i = 0; i <= threads.length; i++){
var messages = threads[i].getMessages();
for (var j = 0; j <= messages.length; j++){
var message = messages[j];
var body = message.getPlainBody();
//email processing//
}
threads[i].removeLable(label);
}