文件名参数

仅在 Linux、macOS、Windows 和 AIX 上支持在回调中提供 filename 参数。 即使在支持的平台上，也不能保证始终提供 filename。 因此，不要假设回调中总是提供 filename 参数，如果它为 null，则有一些回退逻辑。

fs.watch('somedir', (eventType, filename) => {
  console.log(`event type is: ${eventType}`);
  if (filename) {
    console.log(`filename provided: ${filename}`);
  } else {
    console.log('filename not provided');
  }
});

Providing filename argument in the callback is only supported on Linux, macOS, Windows, and AIX. Even on supported platforms, filename is not always guaranteed to be provided. Therefore, don't assume that filename argument is always provided in the callback, and have some fallback logic if it is null.

fs.watch('somedir', (eventType, filename) => {
  console.log(`event type is: ${eventType}`);
  if (filename) {
    console.log(`filename provided: ${filename}`);
  } else {
    console.log('filename not provided');
  }
});