Retrieving Cell Address of Active Cell with onSelectionChange(e) Trigger - google-apps-script

Question

I want to create a script that will display the cell address of the active cell in A1, however, this is proving difficult because I can't even get the onSelectionChange example on the Google Apps Script guide to work. Whenever I run it, the error I get is TypeError: Cannot read property 'range' of undefined.
This is the code:
/**
* The event handler triggered when the selection changes in the spreadsheet.
* #param {Event} e The onSelectionChange event.
*/
function onSelectionChange(e) {
// Set background to red if a single empty cell is selected.
var range = e.range;
if(range.getNumRows() === 1
&& range.getNumColumns() === 1
&& range.getCell(1, 1).getValue() === "") {
range.setBackground("red");
}
}

Answer 1

About your error message of TypeError: Cannot read property 'range' of undefined, I thought that you might have directly run the function of onSelectionChange with the script editor. If it's so, such error occurs because the event object e is not given.
onSelectionChange is used as the simple trigger. In this case, when you want to retrieve the cell address of the active cell with onSelectionChange trigger, please select the cell on Google Spreadsheet. By this, the script is run by the onSelectionChange trigger.
Sample script:
For example, when the onSelectionChange trigger is run by selecting a cell, the sample script that the cell address is put to the cell as the A1Notation is as follows. When you use this script, please copy and paste the following script to the script editor of Spreadsheet and save it. And, please select a cell on the active Spreadsheet.
function onSelectionChange(e) {
var range = e.range;
range.setValue(range.getA1Notation());
}
Result:
When above script is used, the following result is obtained. You can see that in order to run the script, the cell is selected.
Note:
Even when you selected a cell, when the sample script is not run, please close the Spreadsheet and open the Spreadsheet again. In my environment, I confirmed that by this, the onSelectionChange trigger worked.
Reference:
onSelectionChange(e)
Added 1:
About the following your replying,
Thanks. This works and so did the red cell Google example. Although I did have to close the workbook and reopen it to get it to work. How can I set the range to a fixed cell so the active cell address only appears there?
When you want to run the script for only the specific range, how about the following sample script? From your replying, I used your script for this.
Sample script:
function onSelectionChange(e) {
var ranges = ["A2:B5", "D2:E5"]; // Please set the range you want to run the script.
var range = e.range;
var sheet = range.getSheet();
var check = ranges.some(r => {
var rng = sheet.getRange(r);
var rowStart = rng.getRow();
var rowEnd = rowStart + rng.getNumRows();
var colStart = rng.getColumn();
var colEnd = colStart + rng.getNumColumns();
return (range.rowStart >= rowStart && range.rowEnd < rowEnd && range.columnStart >= colStart && range.columnEnd < colEnd);
});
if (check) {
range.setBackground("red");
}
}
In this script, only when the cell in the range of var ranges = ["A2:B5", "D2:E5"] is selected, range.setBackground("red") is run. So please modify ["A2:B5", "D2:E5"] for your actual situation.
If you want to also check the sheet name, please modify above script as follows. In this case, when the cell in the ranges ["A2:B5", "D2:E5"] of the sheet ["Sheet2", "Sheet3"] is selected, range.setBackground("red") is run.
function onSelectionChange(e) {
var sheetNames = ["Sheet2", "Sheet3"]; // Please set the sheet names.
var ranges = ["A2:B5", "D2:E5"]; // Please set the range you want to run the script.
var range = e.range;
var sheet = range.getSheet();
if (!sheetNames.includes(sheet.getSheetName())) return;
var check = ranges.some(r => {
var rng = sheet.getRange(r);
var rowStart = rng.getRow();
var rowEnd = rowStart + rng.getNumRows();
var colStart = rng.getColumn();
var colEnd = colStart + rng.getNumColumns();
return (range.rowStart >= rowStart && range.rowEnd < rowEnd && range.columnStart >= colStart && range.columnEnd < colEnd);
});
if (check) {
range.setBackground("red");
}
}
Added 2:
About the following your replying,
No, sorry. I meant how can I make the active cell address appear in A1. If I click on cell G5, for example, 'G5' appears in A1.
In that case, how about the following sample script?
Sample script:
function onSelectionChange(e) {
var range = e.range;
range.getSheet().getRange("A1").setValue(range.getA1Notation());
}