GAS sends multiple slack notifications - for-loop

Question

I'd like to send notifications to slack using Google Apps Scripts.
It's supposed to happen when any change is made on Gsheet but sometimes the program sends multiple notifications even after only a single change.
I guess my code has any fault or the triggers cause any problem - because I apply this function to more than one sheet.
But it doesn't happen "always", so is it an error caused by GAS specification?
My code is as below. Any idea or advice will be appreciated.
function slackNotification(sheetname,slack_channel){
Logger.log(sheetname)
var mySheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName(sheetname);
var myActiveRange = mySheet.getActiveRange();
var lastRow = mySheet.getLastRow();
var pdfColumn = PDF_column_n
var checkColumn = slack_column_n
Logger.log(lastRow)
var unslacked = [];
for (var i=1; i <= lastRow; i++){
var cell = mySheet.getRange(i, checkColumn);
if(cell.isBlank()){
Logger.log(i + "is not yet notified");
unslacked.push(i);
}
}
Logger.log("unslcked yet"+unslacked)
for (var i=unslacked[0]; i <= unslacked[unslacked.length - 1]; i++){
var pdfCell = mySheet.getRange(extention_column+i)
var checkSlack = mySheet.getRange(slack_column+i)
Logger.log(checkSlack.isBlank())
Logger.log(pdfCell.getValue())
if (pdfCell.getValue() == "pdf" && checkSlack.isBlank() == true)
{
var requestId = mySheet.getRange(request_column+i).getValue();
var clientId = mySheet.getRange(client_column+i).getValue();
var claimId = mySheet.getRange(claim_column+i).getValue();
var groupId = mySheet.getRange(group_column+i).getValue();
Logger.log(groupId)
if (branches.includes(groupId)){
var message = "\nrequestId:" + requestId + "\nclientId:" + clientId + "\nclaimId:" + claimId
var postUrl = slack_channel
var username = 'botbot';
var icon = ':hatching_chick:';
var jsonData =
{
"username" : username,
"icon_emoji": icon,
"text" : message,
link_names: 1
};
var payload = JSON.stringify(jsonData);
var options =
{
"method" : "post",
"contentType" : "application/json",
"payload" : payload
};
UrlFetchApp.fetch(postUrl, options);
checkSlack.setValue(true);
}
}
}
}

Answer 1

Apps Script triggers are bound project-based, not script filed based
If you have multiple functions with the same name in your project - there is no way to know to which one the trigger becomes bound.
Most likely your 5 onChange triggers are all bound to the same function and thus the function is executed multiple times (sending multiple Slack notifications as a result)
It does not make a difference if the functions are located within the same script file or within different script files within the same project
Splitting up your code into different code files is only for visibility/structure purposes, for the trigger the functions are still located all within the same project
Solution
Remove from your project all existing triggers that are bound to functions with not unique names
Give to all functions in your project (not just script file) unique names and save all script files
Install new triggers either programmatically or manually
Now you can be sure that each trigger is bound to a different function
Mind that if the content of your functions is the same (e.g. containing request to send Slack notifications), this content will be executed the same amount of times as the number of respective triggers in your project, so if the content of your functions is identical, you actually need to keep only one function bound to one trigger and remove all the functions of identic content.