Delete Duplicate Row in Google Spreadsheet - google-apps-script

Question

I need this script to delete the row (within the Registration sheet) with the matching Registration Code to the Cancel Registration sheet's Registration code. As of now, this script only deletes a row if "sheetR.deleteRow(i);" is not inside "if (regCodeR === regCodeCR) {}". It doesn't delete the correct row either.
function rD() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheetR = ss.getSheetByName("Registration");
var sheetCR = ss.getSheetByName("Cancel Registration")
var dataR = sheetR.getDataRange().getValues();
var dataCR = sheetCR.getDataRange().getValues();
var headerRow = 1;
for (var i = 1; i in dataR && i in dataCR; ++i) {
var rowR = dataR[i];
var rowCR = dataCR[i];
var duplicate = false;
var regCodeR = sheetR.getRange(headerRow + i, 10).getValues();
var regCodeCR = sheetCR.getRange(headerRow + i, 9).getValues();
if (rowR[9] === rowCR[8]) {
duplicate = true;
}
}
if (regCodeR === regCodeCR) {
sheetR.deleteRow(i);
}
}

Answer 1

I tried this code with simple data having one column with registration numbers. You can modify the main sheet range according to your data. Also make sure to change the sheet names.
Tried and tested the code below :
function deleteDup(){
var mainSheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName('regis');
var cancelSheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName('cancel');
var mainSheetValues = mainSheet.getRange(2, 1, mainSheet.getLastRow(),1).getValues();
var cancelSheetValues = cancelSheet.getRange(2, 1, cancelSheet.getLastRow(),1).getValues();
var k = 0;
var del = [];
// Getting the row index of matching values
for (i = 0; i < cancelSheetValues.length; i++)
{
var cancelValue = cancelSheetValues[i][0];
Logger.log(cancelValue);
for (j = 0; j < mainSheetValues.length; j++)
{
if(mainSheetValues[j][0] == cancelValue){
del[k] = j;
k++;
}
}
}
del.sort();
var count =0;
// deleting the values from the main sheet values array
for (i = 0; i < k; i++ )
{
mainSheetValues.splice((del[i] - count), 1);
count++;
}
var len = mainSheetValues.length;
// Update the sheet with new values
mainSheet.getRange(2, 1, mainSheet.getLastRow(),1).clearContent();
mainSheet.getRange(2, 1, len,1).setValues(mainSheetValues);
}
But instead you can also do this way:
Set a flag value in the registration sheet if it matches with the cancellation sheet.
Then loop through the registration sheet data and delete the matching flag row.
Hope that helps!