Google App Scripts Copy row and Sort range using custom function

Here are the issues why your code is not working:

1. You are using event and r variables in your moveWhenDone() function which is not defined. event and r variables are only accessible in onEdit() unless you pass it as an argument to your moveWhenDone()
2. The reason why your sort function only works on the active sheet is because you used SpreadsheetApp.getActiveSpreadsheet(); which returns a Spreadsheet object. When getRange() is used, it will get the range on the active sheet in your spreadsheet unless you provide the sheet name as part of your A1 Notation (example, "Done!A2:Z")

By the way, I didn't get your point when you mentioned "Don't repeat yourself principle". It somehow contradicts in your statement where "when the dropdown value is changed in sheet 2, after the row has been moved the row should be copied back to sheet 1."

Here is a sample code to move row data from sheet1 to sheet2 and vise-versa including the sorting:

function onEdit(event) {
  // assumes source data in sheet 1 named ASSIGMNMENTS
  // target sheet 2 of move to named DONE
  // getColumn with check-boxes is currently set to colu 7
  var act = SpreadsheetApp.getActiveSpreadsheet();
  var src = event.source.getActiveSheet();
  var r = event.source.getActiveRange();
  if(src.getName() == "ASSIGMNMENTS" && r.getColumn() == 7 && r.getValue() == "Done") {

    // Working but breaks the "Don't repeat yourself" principle
    var row = r.getRow();
    var numColumns = src.getLastColumn();
    var targetSheet = act.getSheetByName("DONE");
    var target = targetSheet.getRange(targetSheet.getLastRow() + 1, 1);
    src.getRange(row, 1, 1, numColumns).copyTo(target);  
    src.deleteRow(row);
    sortSheets()
  } else if(src.getName() == "DONE" && r.getColumn() == 7 && r.getValue() != "Done") {

    // Working but breaks the "Don't repeat yourself" principle
    var row = r.getRow();
    var numColumns = src.getLastColumn();
    var targetSheet = act.getSheetByName("ASSIGMNMENTS");
    var target = targetSheet.getRange(targetSheet.getLastRow() + 1, 1);
    src.getRange(row, 1, 1, numColumns).copyTo(target);  
    src.deleteRow(row);
    sortSheets()
  } 
}

function sortSheets() {
  SpreadsheetApp.flush();
  var sheetNames = ["ASSIGMNMENTS", "DONE"];
  sheetNames.forEach(sheet => {
    var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName(sheet);
    sheet.getRange("A2:H").sort([{column: 1, ascending: true}]);
  });
}

Modifications done:

• I removed moveWhenDone() since I didn't fully understood its purpose to prevent "Don't repeat yourself principle"
• Instead of sorting the sheets every time the onEdit() is triggered, I put the sort function when a row was moved to a different sheet.
• I modified the sortSheets() to loop specific sheets listed in sheetNames variable. I changed the range to "A2:H" because the sample sheet provided has mismatch in number of columns. (ASSIGNMENTS sheet has columns A-Y, while DONE sheet has columns A-M, Hence range "A2:Z" cannot be used)

Sample Output:

If you really want to make moveWhenDone() work, you can pass the event and r variables in onEdit(). Sample moveWhenDone(targetSheet, event, r).

But keep in mind that if you do that, what will happen is that you will basically move the current row twice to your destination sheet.

Example:

• If you changed Assignment 2 to "Done", its succeeding row will also be moved to another sheet. Hence both Assignment 2 and 5 will be moved even if Assignment 5 is not yet "Done"