File System to JSON tree asynchronously in Javascript Chrome App

Question

I have been going at this for hours, but my head is going round in circles and confusing itself with async with callbacks...

I am looking to take a DirectoryEntry in a chrome app and recursively create a JSON file tree, like below:

[{
  name: ent.name,
  path: ent.fullPath,
  isDir: ent.isDirectory
},
{
  name: ent.name,
  path: ent.fullPath,
  isDir: ent.isDirectory,
  children: [
    {
      name: ent.name,
      path: ent.fullPath,
      isDir: ent.isDirectory
     },
     {
      name: ent.name,
      path: ent.fullPath,
      isDir: ent.isDirectory
     }
  ]
}]

In searching I have found many node.js implementations, and have it working in node, but in trying to port it over to FileSystem API and chrome.filesystem in particular, it all goes to pot.

I have also found https://stackoverflow.com/a/21909322 this post which list_dir function is very nearly what I want but it creates a flat structure of all files rather than the structure. I have tried adapting to create the children but cannot get my head around the callbacks.

function walkSync(dirent, cb, listing) {
 console.log('Entering walkSync()')
 if (listing === undefined) listing = [];
 var reader = dirent.createReader();
 var read_some = reader.readEntries.bind(reader, function(ents) {
     if (ents.length === 0)
         return cb && cb(listing);
     process_some(ents, 0);
     function process_some(ents, i) {
         for(; i < ents.length; i++) {
           var obj = { name: ents[i].name, isDir: ents[i].isDirectory};

             if (ents[i].isDirectory) {
                 obj.children =  walkSync(ents[i], process_some.bind(null, ents, i + 1), listing);
             }

             listing.push(obj);
         }
         read_some();
     }
 }, function() {
     console.error('error reading directory');
 });
 read_some();
}

Any pointers to help me get my head round recursion and callbacks to create this would be a great help and reduce the amount of further lost hours.. Thanks!