# 4.3.27 event\_disconnecting

* `reason` (String) 断开连接的原因（客户端或服务器端）

当客户端将要断开连接（但尚未离开其`房间`）时触发。

```javascript
io.on('connection',socket=>{
    socket.on('disconnecting',reason=>{
        let rooms= Object.keys(socket.rooms)
    })
})
```

这些是保留的事件（连同`connect`、`newlistener`和`removelistener`），不能用作事件名称。


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