fetchfor network calls or
fsfor reading files). That's how Olive Helps is able to do things like enforce which domains you can access from your Loop based on your permissions requests. So while we generally encourage you to leverage existing modules/packages/libraries from npm or other sources, you may have to do some testing to make sure it works.
xlsx.read(data, read_opts). However, your Loop would fail with an error if you tried to use
xlsx.readFile(filename, read_opts)because that function would try to access
fs, which isn't available within the secure runtime environment. See Loop Security for more details about Loop permissions and Loop sandboxing.