Google App Script - Function Returning Undefined

Question

I'm trying to call a function that gets a channel ID when given a Slack Workspace and channel name. I can get the correct result within the function, but when I try to call the function elsewhere, it is returning undefined.

Function to get the channel ID `

 //GET CHANNEL ID FROM LIST OF ALL CHANNELS IN WORKSPACE function getChannelID(workspaceName, pageLimit, channelName, nextCursor){ var channelListResponseURL = 'https://slack.com/api/conversations.list'; var payload = { 'limit': pageLimit, 'types': 'public_channel, private_channel', 'cursor' : nextCursor }; var options = createURLargs(workspaceName, payload); var channelListResponse = UrlFetchApp.fetch(channelListResponseURL, options); var channelListJson = channelListResponse.getContentText(); var channelListData = JSON.parse(channelListJson); //iterate through each channel in the returned JSON object and sets the channel ID for the one matching the channelName for (var i in channelListData.channels){ if(channelListData.channels[i].name == channelName){ var channelID = channelListData.channels[i].id; Logger.log('FOUND CHANNEL ID: '+ channelID); return channelID;// IF CHANNEL ID FOUND, THEN EXIT getChannelID FUNCTION AND RETURN CHANNEL ID } } // IF NO CHANNEL ID IS FOUND, THEN CHECK TO SEE IF PAGINATION IS IN EFFECT, UPDATE CURSOR, AND RERUN getChannelID FUNCTION if (channelListData.response_metadata.next_cursor && channelListData.response_metadata.next_cursor != ""){ nextCursor = channelListData.response_metadata.next_cursor; getChannelID(workspaceName, pageLimit, channelName, nextCursor); } else { // IF CHANNEL PAGINATION IS NOT IN EFFECT, OR REACHED LAST PAGE AND NO RESULT IS FOUND return 'No Channel Found in Workspace'; } } 

`

I can clearly see the 'FOUND CHANNEL ID: CXXXXXX' string in the logger, so I'm sure it finds it properly.

But when I call this getChannelID from the main function, it is returning undefined.

  var channelID = getChannelID(workspaceName, pagLimit, channelName, nextCursor); Logger.log(channelID); 

The weird thing is this seems to work when the JSON object from Slack isn't paginated, but when the results are returned paginated, I just seem to get undefined.

Any ideas why the result it's returning is undefined, even though it works in the function?

Answer 1

I think that in your recursive function, the value is not returned. So how about this modification?

From :

if (channelListData.response_metadata.next_cursor && channelListData.response_metadata.next_cursor != ""){
  nextCursor = channelListData.response_metadata.next_cursor;
  getChannelID(workspaceName, pageLimit, channelName, nextCursor);
} else { 
  // IF CHANNEL PAGINATION IS NOT IN EFFECT, OR REACHED LAST PAGE AND NO RESULT IS FOUND
  return 'No Channel Found in Workspace';
}

To :

if (channelListData.response_metadata.next_cursor && channelListData.response_metadata.next_cursor != ""){
  nextCursor = channelListData.response_metadata.next_cursor;
  return getChannelID(workspaceName, pageLimit, channelName, nextCursor); // Modified
} else { 
  // IF CHANNEL PAGINATION IS NOT IN EFFECT, OR REACHED LAST PAGE AND NO RESULT IS FOUND
  return 'No Channel Found in Workspace';
}

Note :

• When channelListData.response_metadata.next_cursor && channelListData.response_metadata.next_cursor != "" is true, no value is returned. So I added return .

If this didn't work yet, please tell me. I would like to modify it.

Added :

In my understanding, when the recursive function is run, the process returns to the line which was run. In order to confirm this, I prepared 3 sample functions.

Function 1

function foo3(value) {
  if (value == "") {
    foo3("bar");
  }
  return "ok";
}

Function 2

 function foo2(value) { if (value == "") { return foo2("bar"); } else { return "ok"; } } 

Function 3

 function foo3(value) { if (value == "") { foo3("bar"); } return "ok"; } 

When these functions is run by as follows,

 var res1 = foo1(""); var res2 = foo2(""); var res3 = foo3(""); 

res1 , res2 and res3 are undefined , ok and ok , respectively.