Trying to getlastrow - google-apps-script

Question

Hello I am trying to have a continual list that copies values from one sheet to another in google sheets. My problem is that it is overwriting on the second sheet. I can't figure out how to find the last row before it inserts values. Here is my code.
function SubmitData() {
var s = SpreadsheetApp.getActiveSpreadsheet();
var sht = s.getSheetByName('Validation')
var drng = sht.getDataRange();
var rng = sht.getRange(6,2, drng.getLastRow(),drng.getLastColumn());
var rngA = rng.getValues();//Array of input values
var rngB = [];//Array where values that past the condition will go
var b = 0;//Output iterator
for(var i = 0; i < rngA.length; i++)
{
rngB[b]=[];//Initial new array
rngB[b].push(rngA[i][0],rngA[i][2]);
b++;
}
var shtout = s.getSheetByName('Track Data');
var outrng = shtout.getRange(2,1, rngB.length,2);//Make the output range the same size as the output array
outrng.setValues(rngB);

Answer 1

I don't see any condition in your code, you're just remapping
function SubmitData() {
const s = SpreadsheetApp.getActive();
const sht = s.getSheetByName('Validation');
const shtout = s.getSheetByName('Track Data');
const rng = sht.getRange(6, 2, sht.getLastRow() - 5, sht.getLastColumn() - 1);
const vs = rng.getValues();
let vO = vs.map(r => [r[0], r[2]]);
shtout.getRange(shtout.getLastRow() + 1, 1, vO.length, vO[0].length).setValues(vO);
}

Answer 2

Here is a modified script, easier to read. If you have the "sheet" in a variable you can call the getLastRow() method. Then plus 1.
You also can push an array inside an array.
Be aware that bad written functions can plus the lastrow. The "" will be see ad NOT empty. For instance:
//BAD:
=IF(A10 = "","","This is not empty")
//GOOD:
=IF(A10 = "",,"This is not empty")
The script:
function SubmitData() {
const ss = SpreadsheetApp.getActiveSpreadsheet();
const inputSheet = ss.getSheetByName('Validation')
const inputValues = inputSheet.getRange(6,2, inputSheet.getLastRow(),inputSheet.getLastColumn()).getValues()
const output = [];
inputValues.forEach(row => {
output.push([row[0].row[2]])
})
const outputSheet = ss.getSheetByName('Track Data');
outputSheet.getRange(outputSheet.getLastRow() + 1,1,output.length,output[0].length).setValues(output)
}