watcher.unref()
- 返回: <fs.FSWatcher>
调用时，活动的 <fs.FSWatcher> 对象不需要 Node.js 事件循环保持活动状态。
如果没有其他活动保持事件循环运行，则进程可能会在调用 <fs.FSWatcher> 对象的回调之前退出。
多次调用 watcher.unref() 将不起作用。
- Returns: <fs.FSWatcher>
When called, the active <fs.FSWatcher> object will not require the Node.js
event loop to remain active. If there is no other activity keeping the
event loop running, the process may exit before the <fs.FSWatcher> object's
callback is invoked. Calling watcher.unref() multiple times will have
no effect.