Add Context Menu Item to SharePoint Online List

Question

I'm adding a Context Menu (ECB) item to a SharePoint Online list using the code example found here.

My code works, the problem is it adds a new item each time the page is refreshed, not overwriting the previously added item, so I get duplicates. How to prevent this?

My code, added via Script Editor on the SharePoint list page:

<script  src="https://code.jquery.com/jquery-3.1.1.min.js"></script>
<script>

  $( document ).ready(function() {
    SP.SOD.executeFunc('sp.js', 'SP.ClientContext', AddCustomUserActionToECB);
  });

  function AddCustomUserActionToECB() {  
    var clientContext = new SP.ClientContext();  
    var oWeb = clientContext.get_web();  
    var oList = oWeb.get_lists().getByTitle('ProjectCommunications');  
    var userCustomActionColl = oList.get_userCustomActions();  
    var oUserCustomAction = userCustomActionColl.add();  
    oUserCustomAction.set_location('EditControlBlock');  
    oUserCustomAction.set_sequence(100);  
    oUserCustomAction.set_title("Add Attachment");  
    oUserCustomAction.set_url("myURL");   
    oUserCustomAction.update(); 
    clientContext.load(userCustomActionColl);
    clientContext.executeQueryAsync();  
  }  
</script>

The result:

How to prevent duplicate entries?

Answer 1

<script src="https://code.jquery.com/jquery-3.1.1.min.js"></script>
<script>

  $( document ).ready(function() {
    SP.SOD.executeFunc('sp.js', 'SP.ClientContext', AddCustomUserActionToECB);
  });

  function AddCustomUserActionToECB() {  
    var clientContext = new SP.ClientContext();  
    var oWeb = clientContext.get_web();  
    var oList = oWeb.get_lists().getByTitle('ProjectCommunications');  
    var userCustomActionColl = oList.get_userCustomActions(); 

    clientContext.load(oList,'UserCustomActions','Title');

    clientContext.executeQueryAsync(function() {
    var customActionEnumerator = userCustomActionColl.getEnumerator();
    var foundAction = 0;
    while (customActionEnumerator.moveNext()) 
    {
        var oUserCustomAction = customActionEnumerator.get_current();            
        if (oUserCustomAction.get_title() == 'Add Attachment') 
        {
            foundAction=1;
            break;
        }
    }   
    if(foundAction==0){
        var oUserCustomAction = userCustomActionColl.add();  
        oUserCustomAction.set_location('EditControlBlock');  
        oUserCustomAction.set_sequence(100);  
        oUserCustomAction.set_title("Add Attachment");  
        oUserCustomAction.set_url("myURL");   
        oUserCustomAction.update(); 
        clientContext.load(userCustomActionColl);
        clientContext.executeQueryAsync();  
    }   
   },
   function(sender,args){
       console.log('Request failed. ' + args.get_message() + '\n' +   args.get_stackTrace());
   });
}
</script>