File System to JSON tree asynchronously in Javascript Chrome App - recursion

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!