A Weird Imagination

Debugging OPFS

The problem#

While the web developer tools in Firefox and Chrome provide a Storage/Application tab for inspecting the local data stored by a web app, neither shows OPFS files there, making it difficult to tell what's going wrong when you have a bug (which was a problem when writting my recent blog posts about OPFS). There's open Firefox and Chromium bugs about the missing feature, so if it's been a while since this was posted when you're reading this, hopefully this is no longer a problem.

Additionally, the tools I did find all use recursion, resulting in them failing to work on the deeply nested directory tree I created by accident.

The solution#

If you don't have several hundred levels deep of nested directories, you can just use this Chrome extension or this script (or probably this web component, although I couldn't get it to install), all named "opfs-explorer".

The following AsyncIterator returns all of the files in OPFS without using recursion and adds properties to include their full path and parent directory:

async function* getFilesNonRecursively(dir) {
  const stack = [[dir, "", undefined, 0]];
  while (stack.length) {
    const [current, prefix, parentDir] = stack.pop();
    current.relativePath = prefix + current.name;
    current.parentDir = parentDir;
    current.depth = depth;
    yield current;

    if (current.kind === "directory") {
      for await (const handle of current.values()) {
                    prefix + current.name + "/",
                    depth + 1]);

And here's the simple HTML display function I've been using that calls that (you will likely want to modify this to your preferences):

async function displayOPFSFileList() {
  const existing = document.getElementById("opfs-file-list");
  const l = document.createElement('ol');
  l.id = "opfs-file-list";
  if (existing) existing.replaceWith(l);
  else document.body.appendChild(l);

  const root = await navigator.storage.getDirectory();
  for await (const fileHandle
             of getFilesNonRecursively(root)) {
    const i = document.createElement("li");
    i.innerText = fileHandle.kind + ": "
                  + (fileHandle.relativePath ?? "(root)");
    if (fileHandle.kind === "file") {
      const content = await fileHandle.getFile();
      const contentStr = content.type.length === 0
                      || content.type.startsWith("text/")
        ? ("\"" + (await content.slice(0, 100).text()).trim()
          + "\"")
        : content.type;
      i.innerText += ": (" + content.size + " bytes) "
                     + contentStr;

The details#

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