Counting entries in a directory

[josephrocca]

Does this API allow for a faster way of counting files in a directory than the example below?

const dirHandle = await window.showDirectoryPicker();
let count = 0;
for await (const entry of dirHandle.keys()) {
  count++;
}

I've been playing around with the API building a bulk file transformer/converter (demo/code) and the above method seems to be a bit slow when there are tens of thousands of files in the directory.

If operating system do track/cache this info then it would be great if it could be exposed in this API.

[slaymaker1907]

Is there anything about the interface that is inherently slow? Also please state which filesystem you tested this on. Windows in particular has weird performance characteristics for its filesystem.

I suspect the perf problem might be because of the excessive number of promises. In my opinion, .keys() should just return an array. If a directory has so many entries that this is bad for perf, the number of promises is also likely to cause perf problems and there should be a separate API which is something like AsyncIterator<Handle[]> so that way the event loop is handling say 50 entries at a time instead of a separate loop iteration and promise per handle. According to the JS spec, new Promise(cb) can't just run cb immediately and is effectively like setTimeout(cb, 0).

[mkruisselbrink]

I think this is a duplicate of #215