I have two volumes. Illustrator is installed on C, my project file lives on D. When I run ai2html against the project file, I get the following errors:

I think this is caused by pathJoin() cutting off the leading slash in docPath (and anything else that is passed to it), causing Illustrator to read d as a regular folder instead of a volume designator.

I've fixed problem locally but I'm unsure if this has side effects elsewhere:

// Similar to Node.js path.join()
function pathJoin() {
  var path = '';
-  forEach(arguments, function(arg) {
+  forEach(arguments, function(arg, i) {
    if (!arg) return;
    arg = String(arg);
-    arg = arg.replace(/^\/+/, '').replace(/\/+$/, '');
+    if (i > 0) {
+      arg.replace(/^\/+/, ""); // leading slash
+    }
+    arg = arg.replace(/\/+$/, ""); // trailing slash
    if (path.length > 0) {
      path += '/';
    }
    path += arg;
  });
  return path;
}

For what it's worth this also brings the method's behaviour in line with Node's path.join().

(Windows 10, Illustrator 27.8)