Split Array Function on Email PlainBody() MSG using Google Script - google-apps-script

Question

I use the following code below to grab emails, get the plainbody(), date and messageto bring them into Google sheet in COLUMN A.
Then in the spreadsheet I copy down the formula in COLUMN C
=ARRAYFORMULA(IFERROR(SPLIT(A3,"|")))
(Which I tested this works as well - not sure if one is preferred)
=SPLIT($A2,"|")
I'd like to combine these functions and have attempted the following
function getEmails() {
var ss = SpreadsheetApp.getActiveSheet();
var threads = GmailApp.search("is:starred in:TanWebOppCRM");
for (var i=0; i<threads.length; i++) {
var messages = threads[i].getMessages();
for (var j=0; j<messages.length; j++) {
var msg = messages[j].getPlainBody();
var dat = messages[j].getDate();
var msgParse = '=SPLIT($A2,"|")';
/*var msgParse = '=ARRAYFORMULA(IFERROR(SPLIT($A2,"|")))';*/
ss.appendRow([msg, dat, msgParse]);
}
threads[i].moveToTrash();
}
}
This DOES "WORK". For example - I know I just sent myself a test email that can be extracted. I know the next row that WILL be appended is Row 30 - and change the code
var msgParse = '=SPLIT($A2,"|")';
to
var msgParse = '=SPLIT($A30,"|")';
Then the extraction works, and you see the split happen.
If I was to import 2 new rows - obviously
$A30 /* stays A30 - so I tried-
var msgParse = '=SPLIT($A[j],"|")';
Just to see if the [j] dynamically changed - even though I know j is for message loop
The question...
how do I get the following line to increment to the append row value
so that each loop changes the row reference to the appended row - so if I was starting from row 30
var msgParse = '=SPLIT($A30,"|")';
var msgParse = '=SPLIT($A31,"|")';
var msgParse = '=SPLIT($A32,"|")';
Is what the incremental msgParse value data would be.

Answer 1

You can construct the formula via string concatenation.
If you always just append you can just get the last row and add 1 (because the new row will be one row below) and use that as the row reference:
var msgParse = '=SPLIT($A' + (ss.getLastRow() + 1) + ', "|")';

Answer 2

Since I'm new to Script - and I couldn't find this answer - I wanted to add my own answer.
#Robin definitely pointed me in the right direction - I didn't realize I can use string concatenation - however the solution provided did not increment and once that string concatenation was written - it remain for the rest of the FOR loop
The final piece was adding a counter - I could probably eliminate the first row = variable and there is probably a way to make this more efficient But it took in 20 sample emails from gmail and parsed them into spreadsheet in maybe 6 or 7 seconds.
function getEmails() {
var ss = SpreadsheetApp.getActiveSheet();
var threads = GmailApp.search("is:starred in:TannerWebOppCRM");
var row = ss.getLastRow();
for (var i=0; i<threads.length; i++) {
var messages = threads[i].getMessages();
var newrow = row + 1;
for (var j=0; j<messages.length; j++) {
var msg = messages[j].getPlainBody();
var dat = messages[j].getDate();
var msgParse ='=SPLIT($A'+ (newrow) + ', "|")';
ss.appendRow([msg, dat, msgParse]);
newrow = newrow + 1;
}
threads[i].moveToTrash();
}
}
To complete this post I wanted to include the update and addition to the answer I accepted because that technically answered my question - just didn't put it into context how to make it work in my script.