#Triggers.gs

var C_SOURCE_TRIGGER = 'SPREADSHEETS';

/*
--------------------------------------------------------------------
   _____      _     _______   _                       
  / ____|    | |   |__   __| (_)                      
 | (___   ___| |_     | |_ __ _  __ _  __ _  ___ _ __ 
  \___ \ / _ \ __|    | | '__| |/ _` |/ _` |/ _ \ '__|
  ____) |  __/ |_     | | |  | | (_| | (_| |  __/ |   
 |_____/ \___|\__|    |_|_|  |_|\__, |\__, |\___|_|   
                                 __/ | __/ |          
                                |___/ |___/                     
--------------------------------------------------------------------
*/
function setTriggerOnEdit(nameFunction)
{
  if (checkTriggerExists(nameFunction, C_SOURCE_TRIGGER)) { return -1; } // trigger exists
  var ss = SpreadsheetApp.getActive();
  ScriptApp.newTrigger(nameFunction)
    .forSpreadsheet(ss)
    .onEdit()
    .create();

}



/*
  USAGE
  
  var exists = checkTriggerExists('test_getSets', 'SPREADSHEETS')

*/
function checkTriggerExists(nameFunction, triggerSourceType)
{
  var triggers = ScriptApp.getProjectTriggers();
  var trigger = {};

  
  for (var i = 0; i < triggers.length; i++) {
   trigger = triggers[i];
   if (trigger.getHandlerFunction() == nameFunction && trigger.getTriggerSource() == triggerSourceType) return true;
  }
  
  return false; 

}