Google onEdit Script for multiple columns drop downs - google-apps-script

Question

I have some script that allows me to select multiple items from a drop down in google sheets. I have the below script which works fine for column L(12) but I want this to also work on column M(13) and N(14). I have tried || (as in OR) which then makes all the drop downs in the sheet also allow multiple selections which I don't want. Can anyone help me with this?
function onEdit(e) {
var oldValue;
var newValue;
var ss=SpreadsheetApp.getActiveSpreadsheet();
var activeCell = ss.getActiveCell();if(activeCell.getColumn() == 12 && ss.getActiveSheet().getName()=="Client information"){
newValue=e.value;
oldValue=e.oldValue;
if(!e.value) {
activeCell.setValue("");
}
else {
if (!e.oldValue) {
activeCell.setValue(newValue);
}
else {
if(oldValue.indexOf(newValue) <0) {
activeCell.setValue(oldValue+','+newValue);
}
else {
activeCell.setValue(oldValue);
}
}
}
}
}
function myFunction() {
}

Answer 1

You need to make sure that those columns should be within the range of the statement as what dared provided as an answer. column should be within 12 and 14 inclusively.
Additionally, I have made some modifications to make use of the event object instead of SpreadsheetApp and improved your if-else block.
Code Modifications:
function onEdit(e) {
// Spreadsheet object can be retrieved from event via e.source
var sheetName = e.source.getActiveSheet().getName();
// Range object can be retrieved from event via e.range
var range = e.range;
var column = range.getColumn();
if (sheetName == "Client information" && column >= 12 && column <= 14 && e.value) {
var newValue = e.value;
var oldValue = e.oldValue;
// first if statement is the default behavior, no need to include
// the else statement is now combined on the outer if statement
if (!e.oldValue)
range.setValue(newValue);
else {
if (oldValue.indexOf(newValue) < 0)
range.setValue(oldValue + ',' + newValue);
else
range.setValue(oldValue);
}
}
}
Output:

Answer 2

function onEdit(e) {
// cache the column number
let col = e.range.getColumn()
if ( e.source.getActiveSheet().getName() === "Client information" &&
col > 11 && col < 15) {
// This block will run if any of the columns L, M or N are edited
// If you need different behaviour depending on which column was edited test the column number
// Column L
if (col === 11) {
// This block will run if column L is edited
}
}
// Without seeing the type of data you are working with I'm unclear on what
// your old and new values represent.
}