Getting X is not a function when using getWorkflowStaticData with sets

I am having difficulty polling an API for new IDs based on this workflow that I had found:

My understanding is that I need to get the global static data for a given workflow, and if a set which holds the IDs which have already been posted to Discord or in the above example doesn’t exist, then I have to update the set for static data so it persists in the next run.

This is something like:

const staticData = getWorkflowStaticData("global");

if(!staticData.postedIds) {
  staticData.postedIds = new Set();
  // Add found Twitter IDs from the previous node to staticData.postedIds
  // Return empty array so the next node where I post to discord doesn't post a bunch of IDs since postedIds was undefined so there were no previous executions
  return [];

// Code here runs on next execution now that staticData.postedIds is a Set
const toPost = [];
// Check if new IDs have been posted
for(const tweet of items) {
  if(!staticData.postedIds.has( {
    // Make sure the new ID is saved to postedIds so it doesn't get posted in the future
    // Add to toPost array so that the next node will post the ID to Discord or or whatever
    toPost.push({json: {id:}});
return toPost;

With this code, what happens is the line with if(!staticData.postedIds.has( { fails for me because staticData.postedIds.has is not a function even though I had previously made the check and created a set in a previous execution. To be clear I am not manually executing the polling workflow I’ve made. I’m not exactly sure what is going on to get this error. It seems that if I use sets that it doesn’t seem to work with getWorkflowStaticData. This seems to apply to maps as well as I have tried those before in a different scenario too. However, when I use arrays it works just fine.

Unfortunately I cannot post the exact work I have done but hopefully this is a good enough explanation of my issue.

From a very quick check, the vm2 lib used by the Function node returns an empty object when creating sets and maps. The workflow you linked to filters using arrays, so I would advise to try the same approach.

Ah understood. That would explain why it doesn’t work. Still, hopefully if anyone else runs into this problem they’ll find this post now! It took me quite a while to figure out that I can’t just store anything (maps, sets) in the workflow static data.