Recursively loop through node tree and check if a node exists, if not, create it using callback or p

I want to write a function that recursively browses a node tree and depending on if a certain node exists, either log its values or create the missing node. This should be fairly simple but I can't seem to wrap my head around it.

my code currently looks like this:

let folderName = 'My Folder Name';

function init() {
  let hasFolder = false;
  let folderId = '';

  chrome.bookmarks.getTree(function(itemTree){
    itemTree.forEach(function(item){
      processNode(item);
    });
  });

  function processNode(node) {
    // recursively process child nodes
    if (node.children) {
      node.children.forEach(function(child) { 
        processNode(child); 
      });
    }

    if (node.title == folderName) { 
      console.log(folderName + ' folder already exists: ID is ' + node.id);
      hasFolder = true;
      folderId = node.id;
    }
  }
}

It's working fine for outputting the node ID if the folder already exists, but now I want it to create the folder if it doesn't. I figured I'd need to use a promise or callback. The code to create the folder is simple:

function createFolder() {
  chrome.bookmarks.create({
    title: appName,
    url: null
  }, onBookmarkAdded)
}

How and where would I integrate that into my current function? (init() is called on first install of the app.)