google-apps-script multiple criteria writing over headers - if-statement

Question

I have taken a bit of script from Serge which is great (original link here. I have added in a second criteria to exclude certain rows and it works great except, if there is not header in the sheet being copied to, it will not work (error: "The coordinates or dimensions of the range are invalid.") and if I enter a header or some other data, it overwrites it. Can anyone assist please? I have also found that is there is no match to the criteria I get following message "TypeError: Cannot read property "length" from undefined."
Also, what change would I need to make to change the cell 'dataSheetLog[i][12]' to the status variable, i.e. "COPIED" after I have copied it across. I have tried writing a setValue line but it is obviously the wrong instruction for that syntax.
Code is:
{
var Spreadsheet = SpreadsheetApp.getActiveSpreadsheet();
var sheetLog = Spreadsheet.getSheetByName("LOG");
var sheetMaint = Spreadsheet.getSheetByName("MAINTENANCE");
var Alast = sheetLog.getLastRow();
var criteria = "08 - Maintenance"
var status = "COPIED"
var dataSheetLog = sheetLog.getRange(2,1,Alast,sheetLog.getLastColumn()).getValues();
var outData = [];
for (var i in dataSheetLog) {
if (dataSheetLog[i][2]==criteria && dataSheetLog[i][12]!=status){
outData.push(dataSheetLog[i]);
}
}
sheetMaint.getRange(sheetMaint.getLastRow(),1,outData.length,outData[0].length).setValues(outData);
}

Answer 1

In:
sheetMaint.getRange(sheetMaint.getLastRow(),1,outData.length,outData[0].length).setValues(outData);
getLastRow() refers to the last occupied row and should be ,getLastRow() + 1,to keep from overwriting your headers and other problems.
Edited:
{
var Spreadsheet = SpreadsheetApp.getActiveSpreadsheet();
var sheetLog = Spreadsheet.getSheetByName("LOG");
var sheetMaint = Spreadsheet.getSheetByName("MAINTENANCE");
var Alast = sheetLog.getLastRow(); // Log
var criteria = "08 - Maintenance"
var status = "COPIED"
var dataSheetLog = sheetLog.getRange(2,1,Alast,sheetLog.getLastColumn()).getValues(); //Log
var dataSheetLogStatusRange = sheetLog.getRange(2,13,Alast,1); //Log
var dataSheetLogStatus = dataSheetLogStatusRange.getValues(); //Log
var outData = [];
for (var i =0; i < dataSheetLog.length; i++) {
if (dataSheetLog[i][2]==criteria && dataSheetLog[i][12]!=status){
outData.push(dataSheetLog[i]);
dataSheetLogStatus[i][0] = "COPIED";
}
}
if(outData.length > 0) {
sheetMaint.getRange(sheetMaint.getLastRow() + 1,1,outData.length,outData[0].length).setValues(outData);
dataSheetLogStatusRange.setValues(dataSheetLogStatus);
}
}
}
what change would I need to make to change the cell
'dataSheetLog[i][12]' to the status variable, i.e. "COPIED" after I
have copied it across.
You were trying to update the value in the array that was extracted from the sheet and not the sheet itself. As arrays are zero based and spreadsheets are not, to translate, +1 must be added to array row and column indices. I am assuming status is in column M of your sheet.